First bike build

Hello!

I am excited to build my first bike, a Gary Fisher Tassajara from 93. So far I have the frame and fork.
I am writing here to hear your opinions, tips and tricks. I think it’s a bit hard to start and everything is so connected so I just need a good place to start.

I did not expect to be so overwhelmed by the possibilities and how the costs would differ. I bought a cheap Araya rim brake wheel set from the kind person I bought the frame from. It’s in okay condition, true, but not running 100% clean.

On that wheel set there is only space for a 7s casette. So either I go 3x7 or 1x7. I am thinking of buying a 11-28 casette for that.

Initially I wanted to go with a 1x9 setup. I still consider buying new wheels to make that happen (mavic crossroad rim brake wheel set I think). However, I guess I should try to work with what I have? Also that money would be well put into bike bags for bikepacking.

I know 1x 7 is very limiting for a mountain bike but I live in Denmark, so the climbs don’t really exist and I’d use it a lot in the city. Nevertheless, if I would like to bring the bike elsewhere having the 3x7 would be nice (thinking xt crank from the 90s). I don’t count the grams too much. Now I am surprised at the cost of working 3x7 deore or xt shifters and how hard it is to find them. Yes, I know about DBA and Ebay and Vinted, yes I already have saved searches there.

If I do a 1x7, what chainring size would you recommend? 44t? I hate having too much cadence on a flat street.

What starting point should I choose?
Thank you for your time. All answers are appreciated.

PS: I have a bike that is up and running, so it is okay for me if this build takes some time. I want to use quality components.

All the best
J