OH, now i remember what i meant to ask!

Should i spent my +s on weapon or eilodon(because both are good, but there is possibly one better than the other at an early stage of the game)

Now you mention 2000 base stats eilodon... how do you calculate the base stats? i'm liooking at the wiki at the list of all SSR eilodon, do you mean Maximum HP + Maximum Attack?

In that case only the lilim fail to pass that( by only 1992 Max Base stats)

The only ones on top of Belial (if we go with Max Base stats) are the Kaiser Dragoons(4200) and Kirin(3342) while Belial(3300). And since you said only 2000+, i guess that the answer to my question is: Yes, use the +s on Belial.