Kid Buu was first, then Fat Buu, then Evil Buu vs Fat Buu, then Super Buu as he's been deemed, Gotenks+Piccolo Buu, Goten + Trunks + Piccolo buu (seen right before Gohan absorb), Gohan Buu, Everyone absorbed Buu (after he absorbs Vegetto), Kid Buu, Ubuu
At least...that's what I think it is