What advice would you give to a new collector?

Find another hobby.

Read this first…

https://www.watchcrunch.com/Aurelian/posts/does-your-collection-have-a-theme-7552

I am all about the dials. Buy the watch that speaks to you. 

IMO, diversity is key.

I have 11 watches with two incoming, so 13 total.

12 brands from six countries, seven microbrands, six major brands, nine colors, seven divers, six non-divers, five on bracelet, five on rubber, 2 on leather, one on NATO.  

Basically, I'm fully covered.  I do still want one chrono and one German watch, but we will see.

Learn first, pick a theme, learn A LOT MORE, then buy.

If you MUST have a watch to start, get the best you can afford that fits best into your projected life for the next 5 or so years that will also fit your theme.

Shop the size first and then the one that jumps off the counter and grabs you in your comfortable price range. 

To buy a normal, cheap-ish watch that's not too out there, I would start with a dresskx. In order to learn about watches but mostly what I like and don't like, size, color, style, etc.

A few points I'd pass on to someone starting out. 

1.  Go slow, it's a marathon not a sprint. There is no need to buy one of everything that looks interesting. You will need time to refine your tastes, so take the time to look at lots of watches before buying. 
2.  Have a budget and stick to it. 
3.  Be realistic about your lifestyle, and what you will wear. i.e. If you don't dress up often, you're unlikely to wear a dress watch often. Therefore, it's likely better to start with a diver/field/sports/pilot's watch. Add a dress watch later, if you decide you want one. 
4.  Don't buy something (brand, style, particular model, etc.)  just because the watch community says "everybody needs a ____". Like seriously, you don't need to buy a Seiko to start... 
5.  Like @VictorAdameArt said, keep the first watch relatively simple. A three hander with a date, maybe a day/date, a conservative style, and a relatively conservative colour. More interesting watches will come, but starting out it's likely best to stick closer to more conventional styles and colours. 
6.  Quartz watches are great, and should not be avoided. If you've never worn a watch before, quartz is likely the perfect starter. 

Bonus: A field/pilots, or "everyday" watch is likely a better starter than a dive watch. Something like a Vaer S5/C5, is a pretty easy way to get into a new watch that will be comfortable, affordable, and durable.  

Ditto.  I think you said it all.

Start your collection with a vintage Oris pin-lever.

Try your first few watches in before you buy them. Just starting out you won’t know how to judge sizes and weights so try them and don’t just buy nice looking ones online. 

We are all gonna give rational and sensible advice that you will ( and should) probably ignore. You're gonna buy a lot of watches at first. You will think each time..yeah, this is the one and then you'll be back on YouTube hunting. You will regret a few and love many. No matter how long you are in the game, the hunt is probably the most satisfying experience. The fleeting moment of opening a new box being the pinnacle...followed by watching more reviews on the watch you just bought. Just have fun...know you'll blow some money, but you WILL refine your taste as you go. I don't think you can get "there" by just doing a bunch of research and buying one watch for life. If you were that kinda guy, I doubt you'd be on this website! Happy hunting!!

Like any hobby, I would say enjoy the ride - learn, explore and be honest with yourself. After doing this for quite awhile, I’ve become very selective of what I buy due to experience and figuring out what‘s important to me in a watch.

Do research before you buy! my grand father told me it is not necessarily be expensive instead the watch look and movement should speak to you. It’s like buying a crystal from a shop. I would highly recommend to start collecting watches under 1 k budget first. Then eventually grow your collection based on your interest and research. showing up in your local ADs once in 2-3 month is a good idea to build relationships for future reference. 

Don’t be too impulsive (I’m trying to remind myself this as well)

The best way to learn is to make mistakes, pay the price, and move on

Other than that, I would recommend buying something in the € [1000-1500] range (Sinn556, Nomos Club, Damasko DS30, Longines Conquest, Mido Ocean Star, Alpina STARTIMER PILOT AUTOMATIC...), with some brand cachet, a good movement, something you can connect to easier than with the latest microbrand producing watches in an undisclosed location.

If you enjoy the experience, welcome into the watchfam, you're ready for more and higher end watches (and irritating searching for that flying springbar when you make an ill-advised last minute strap changing decision 😊)

If you don't, not the end of the world, you can resell your watch easily without losing your shirt and pick up another hobby.

This is the advice I got when I was into guitars:

Buy what looks good to you. If you become invested enough to research into it, then great. You'll come to understand the different sounds, how to change the pick ups, how to fiddle with the amp, etc. Your taste in music will change along the way too. If you think your guitar can't handle what you want to play, buy a new one/replace it.

Same advice I believe mostly applies to watches too. Buy what you like, if you like it enough you will learn about the different design types, movement types, etc. You can go from there, or you can have that one watch collection.

Also, buy within budget. If your first watch can be an Omega/Rolex/AP/etc. by all means, go for it.

Patience and delayed gratification

Buy a watch that speaks to you and you alone.  

Don’t buy a watch to try to make a statement to others.

Start affordable to experience a watch and see what you like you don't like and what matters to you. Then take it slow, learn, set goals, prioritize.

Buy what tugs at your heart strings but don't buy the cheapest 1 or the 1st 1.

You can get in and out of a lot of preowned watches without committing a ton of money, but buy the seller.

Buy what you like for whatever reason you have and enjoy your watches in any way you wish with out apology. There is never a reason to bedowngrade someone else's collection. We are all different and that's a good thing.

IMO, Watches don't have to be expensive or special to anyone but you. One of my favorite watches cost the princely sum of $37 but it's comfortable, looks great and makes me smile. No explanation needed. Enjoy your hobby. 

Always try before you buy. Always.

I think most of us are on the same page when it comes to advise for newbies. Here's my two cents from my profile's Q&A: "Take your time before making the first more substantial purchase: Get your hands on as many iconic pieces (maybe even homages...) as possible and determine what REALLY speaks to you, once it's on your wrist. Building and refining one's taste early on will greatly reduce the risk of buying unwisely."

Take myself as an example: I've always thought that I loved the Daytona. Got me a Pagani Homage plus managed to spend a few hours with a friend's genuine Daytona in white gold. And guess what: It turned out the Daytona doesn't do it for me. I even figured out that I'm not much of a chronograph guy (thank god!). Alas, I also noticed how good precious metal feels on the wrist. Woe is me... 😑

Wise piece of advise, but it takes some experience in the watch game to actually follow it. Otherwise, there would not be 900.000 people buying a Rolex watch each year

run!

…towards the light of the nearest watch boutique!

I would say do the opposite. Buy all the cheap cool looking watches you enjoy, price doesn't correlate to aesthetics but it may occasionally mean greater quality.

1. Don’t buy a watch that you like or want too quickly. Give yourself a couple of weeks or months to see whether you really like the watch.
2. Try the watch where possible. The pictures and dimensions don’t fully translate to how the watch will sit on your wrist. 
    
3. It‘s a hobby, don’t get too serious about it. Have fun!