This phrase is indicating you don't have something, whether it's parents, drugs, money, llamas, a life, a brain, friends girls (or boys, not here to judge..... :/ ), a sense of humour or if you just want to cuss someone out and you have nothing to lead from
A 'fucked up nigga' is someone who got rushed by multiple roadmen and comes out looking like a guy who got run over by a bus. For emphasis you can extend the 'fucked' into fuuuuuuuuuuckedd.
Likened unto "Keeping it Real" or "Keeping it One Hundred", "Keepin it One Dollar" means that you are being all the way truthful with yourself and others, without consideration for the consequences of your actions
Dope Boy 1: D-Loc was just "Keepin It One Dollar" when he talked that shit on Big Uncle Snoop Dogg.