-1000 trade just means they don't think that's a good trade, you'll have to give more. And hover over it, some things they'll never be willing to trade, but it'll say that if you hover over it.
Generally making friends is most easily done with a Guarantee independence as Biowraith said, followed by a NAP and then a lot of gifts once they hit trust cap, eventually making alliance possible. Xenophobes have a lot of negative acceptance modifiers to more important pacts though, which aren't as easy to overcome as opinion modifiers, they'll have negative relationship from being Xenophobes which gives negative acceptance, and have straight up negative acceptance from being xenophobes, and more often have personality types that have negative acceptance. Overcoming all of that is hard to impossible often, it's rare to make close friends with xenophobes unless there's a existential threat to drive you two together or at least some very close common ground. (Like being spiritualist.) And if possible you'll want to do this before you actually have borders with them, otherwise friction will drive you apart (and right NOW if the AI starts putting claims on your systems that's basically any diplomacy possible with them gone for the rest of the game unless you give them those systems. Having systems claimed by others gives a quite large permanent negative opinion modifier. I hope they add the ability to get others to revoke their claims eventually, preferably though diplomacy.)