Your first winning run
Build around what the shop offers, and stop spending once you can beat the next blind.
Read the run, then pick a hand
Start by finding a hand you can draw reliably. Pair is easy to repeat; Flush pays more at level one but usually asks for more discards. Let your first useful Joker decide which direction to take.
Buy enough score
A simple source of Chips or flat Mult can carry the early blinds. Once your regular hand clears a blind comfortably, save money for stronger scaling and later shops.
Check the boss before shopping
Read the upcoming Boss Blind before committing to a suit or a single hand type. Keep a backup plan if the boss disables the cards you normally rely on.