What about throwing mathematics and GTO out if the window and recheck your own success?
If you already have some volume and HM, you could filter for this spot (Hero calls 3bet pre ip/oop).
Look at the hands that are winning for sure and seem to bee loosing.
Cut out the last category and look for hands that are on the edge.
Start studying this category of hands and look out for mistakes and problems.
Play and elaborate this category on a decent volume. Start experimenting with hands.
If you work out Ranges like this, you can take your own skill level and pool exploits into account.

There are already good preflop charts out there. As a micro player i would NOT spend (waste?) any time looking into this yourself. Get some good charts and learn to play slightly different than/deviate from those charts as exploits. You can work with equilab after

I made a couple videos about designing preflop ranges way back in the day (some of my first videos on RIO I think.) Understanding some basic theory principles is useful but ultimately you'll probably want to do some mix of what droid and raoul recommended above.

Generally you need about 35 percent equity with cards that can flop nut hands and about 45 with offsuit broadway types against a 3-bet range. You can make an adjustment of minus 5 percent if you’re out of position. It’s not perfect but is going to be really close to solver ranges