multiple bat configurations

being budget minded (cheap if u will) i'm looking for suggestions of lites to start my flashaholic journey that will take a variety of bats so i don't have and excess of either floating around until i know a little bit more about the subject.

smallish aa, 123, 14450

medium 123, 18650

large 18650, 26550

it doesn't make any difference if theres extenders, holders, or whatever is involved to make combinations work. form follows function.

from your experience and expertise to my ear.