It’s got to be Sessions. Nobody else is in his league. He is a sitting U. S. Senator and has proven himself under fire supporting Trump.
We know Trump is not ideological at all, which is why he immediately endorsed a gun control measure right after Orlando in which the NRA had to publicly rebuke him.
His VP will have to be nonSouth and a bit younger. That means Kasich or someone from another state in the Midwest. I can't stand Kasich, but if you have no money, you are going to have to do something to appeal to voters who don't like you. He will have to choose someone who knows how to get a bill passed, so it will have to be someone who has experience in Washington.