Welcome to the forum, Javel! We’ve followed similar paths, you and I, as far as the hobby goes. I built mostly Monogram airplane and armor kits as a kid, moving up to Tamiya armor just before I graduated from high school (in 1982). I also built Revell ships, as well as kits in other subjects from various makers.
Coming back in around 1999, I started out again with Monogram airplanes, though I’ve branched out to other subjects.
As far as good online sources go, there are several, and you may wind up using several. Here’s a short list of sources I use:
Squadron:A broad range of kits and supplies, though if you get into more specific or obscure subjects, you may not find it here. But always a good place to look
Sprue Brothers:Good selection of kits and supplies, frequent sales with e-coupons or discount codes sent out to their customer email list
Freetime Hobbies:Online hobby shop based in Georgia (USA).
MicroMark:Large selection of hobby tools and supplies, from model railroad supplies (very useful for us, too) to scale modeling supplies
As far as kit sources go, the second-hand market is a good place to look, too, whether it’s for a classic Monogram kit, or a newly-issued kit from a contemporary maker. I have bought a lot of kits off eBay, as well as at model shows and through trades and raffles at our club (Delaware Valley Scale Modelers).
Also, if there are no dedicated hobby shops near you, you might still look for the arts & crafts chain stores. Michael’s, AC Moore, and HobbyLobby all carry supplies that we can use, even though they aren’t dedicated model shops.
I hope that all helps, and I look forward to seeing your builds!
Best regards,
Brad