best affordable watches?

I'm going to disagree with the preowned Omega advice. even at the top end of the range you're going to be looking at stuff that's 20+ years old and possibly quite a bit older, plus the cheaper you go the greater the possibility of getting an utter turd gets.  Additionally, you'll own a vintage watch, with all the pains around service and lack of waterproofing that that involves.  Don't get me wrong, I love my 62 Seamaster, but it is not a watch for the uninitiated.

OP: Watches basically come in two flavors: 'automatic' [or 'manual'](all gears, wound by an internal rotor that gets it's energy from you wearing it) and quartz (battery powered, like your four function calculator)  The people who don't care will be oblivious to quartz, and quartz will keep great time for years no matter what you do, but watch snobs will eviscerate you for it in most circumstances. (I've got  nice quartz and 'mechaquartz' quartz chronographs)  A good automatic may be off by a few seconds a day straight from the factory, and it will just plain stop if you don't wear it for a few days, but it is an insane feat of engineering to have nothing but gears and springs tell time, which is why all the expensive watches are manual.

I'm going to throw out a few watches towards the low/mid end of your range or maybe even below that may work reasonably for you.  $500-1500 is a bit of a dead zone as others have said.  It's too cheap for a true high end, but the watches that aim to get 90% there as a good value are beginning to peter out at that point.  My recommendations are going to be all new since there's so much going on in the used market that you can't really put good numbers on things easily.

Dress Watch--A watch specifically designed for the office. Don't wear it on weekends, don't wear it swimming. It's job in life is to look nice:

Tissot Gentlemen Powermatic 80 - $750ish. A nice swiss watch with an 80 hour power reserve (it'll keep on ticking for 80 hours when you take it off your wrist if it's fully juiced up)  Modest styling, and screams "I wanted a swiss watch, and this is the best I could get."  Good looking watch, and the 80hr reserve is very good (normal is ~40hr) but you will scream 'entry level analyst' https://www.tissotwatches.com/en-us/t1274071104100.html 

Islander ISL-38 or -39 "SARB-Just" - $350.  Below your price range, but a very nice little watch from a microbrand based on LI.  Sort of a mash-up of the Seiko SARB (discontinued highly regarded $1000 dress watch) and the Rolex DateJust.  The quality is impeccible and the movement is very good even if it only has a 40 hour reserve.  If you're willing to own it it will treat you well.  Your choice between Grey or Blue sunburst dials.  There are also Black, Salmon, and "Don't call it Tiffany Blue" dials out of stock. https://longislandwatch.com/islander-hi-beat-automatic-dress-watch-with…

No link here, but the Seiko 5 SNKL23J1 is also a steal at about $120 if you have a small wrist.  The watch band is crap and you need to shell out $30 or so for a decent black leather strap but after that it looks very decent.

Field Watch - An outgrowth of army watches.  It can be classed up for all but the most formal occasions or dressed down for suburban gardening:

Hamilton Khaki Field Automatic - $625.  Can't do much better than this. same guts as the Tissot mentioned earlier, cool story and case (american/swiss company) Get it on the steel bracelet for formal events.  It takes two minutes to put on a leather or plastic strap.  Be careful not to get the "mechanical" instead.  That's more of a true army watch and not really office appropriate. https://www.hamiltonwatch.com/en-us/h70455133-khaki-field-auto.html

Diver - What the name implies.  Really easy to read if you're underwater in low light or just bleary eyed from staring at a spreadsheet for the past 18 hours.  Very waterproof too.

Several years ago a Seiko SKX-007 or -009 would have been the easy answer at $200, but they're out of production now.  there are a number of knock-offs/homages though and they're almost always under $500.  Just make sure to get it on steel, not plastic if you're going into the office.

Chronograph - A combination watch/stopwatch  Super intricate, but can be very cool.

Buahaha, hahaha. No way you're getting a good new mechanical chronograph in this price range,  you either need to move towards used or go quartz.  Nezumi and Dan Henry have some really nice 'mechaquartz' models that are worth looking at, and there are decent other options, but don't go mechanical here.