Well, what's good is that since you're only at Goldenrod then you don't need a full team of 6 unless you really want it. whenever I do playthroughs, I always seem to have a team of 3 or 4 until I get closer to the end.
For your team for the playthrough, I'd suggest Quilava, Bellsprout, and Poliwag, although you could have Wooper instead of Poliwag. I'm only gonna recommend Poliwag because in my experience Polywrath has been more useful than a Quagsire. For your 4th slot, pop in your rattata and teach him the HMs that you need instead of wasting a spot on one of your mains.
You could put Zubat on your team, because if you can make it a Crobat, it will outspeed everything and it's amazing how powerful it can be.
Within the next few routes you may find Sudowoodo useful on your team, and in Goldenrod if you talk to Bill (he should just be in a house) then you can get an eevee. Adding those two are totally up to you, although I'll restate that I personally only use a few pokemon that I train up to be a high level at the start.
So yeah, in short, right now, make your team Quilava, Bellsprout, Poliwag, and keep rattata around for the HMs.