No worries, welcome. For cash games, theres usually a min and a max. Min, cause its annoying if someone buys in for $1 and goes in everytime; max, to limit exposure and the game size. Usually the max is anywhere between 80-200 big blinds ( so if Im playing 5cent/10cent, 200bb is $20, capisce?). There's also, "half the big stack" or matching the big stack, so if someones winning tons and has $100 in front of them, new players can buyin for half that instead of 20. Personally I dont do this, match the stack makes it more dangerous for newer players.
Cash should be relaxed. If you buyin for 5 you risk 5, if you buyin for 20 you risk 20. Most people cite the big blind when figuring out mins and maxes; 50bb is short stack, 200bb is deep stack.