Arjuna or elizabeth

well i guess arjuna since he is a reliable aoe archer and he is better than atlanta

If your roster lean heavily towards female servants then raise Elizabeth first and you're gonna raise both of them eventually.

Elizabeth is actually semi-decent support, I'd suggest raising her first.

I've actually had both since I started playing FGO. I personally preferred Arjuna to Liz, not only because he's SSR, but because I found Liz to be not as generally useful. Arjuna can hit pretty hard and his NP is really strong. I usually stick a black grail on him because Hero of the Endowed basically negates the demerits.