Last run:
Mediocre player on Normal using Indigo Dipole
When I say "buy from", I tend to mean "buy all objects which give permanent stat boosts".
Floor 1: Buy from cheap shop. Skip all others, lacking credits and/or keys. Pick up skeleton key from sacrifice shop.
Floor 2: Buy from cheap shop, skip all others (still lacking credits), although I did visit them since I had the skeleton key and they occasionally have breakables in them.
Floor 3, 4: Buy from cheap shop, weapons shop, robot shop. Visit defensive shop, but most of the stuff in there is, how to put it diplomatically, crap. "Reduce movement speed by 50%", how about no.
Floor 5: die