How can i tell if im celtic or Slavic etc.....?

i was adopted so i have no clue of my heritage. i know my parents last names which were of italian and spanish decedents but then again im still not very sure if the guy on my birth certificate is my dad anyways besides the point. i know between celtic Slavic and whatever others there are there are different characteristics and physical features. im 5'7" kinda like jlo carmel skin ,not that i look anything like jlo :( . my twin bro get darker then me tho. but its weird because we will get all tan like were some kind of latin or whatever but then we get all albino in the winter like were all white. we have brown hair kind of carmel color as well blue green eyes. my twin is tall over 6ft, big lips i think my nose is big too not that it could have anything to do with ethnicity. anyways sorry that this is so long and i know your answers are only a guess but ide love if you could say what you think i might be descendant of maybe not the exact region of course lol but like in the question celtic salvic etc. i know your probably think why don't you get a dna test or something. well to answer your question im broke but when i have money to do so i will :D