Die to live from alien love secrets(a very worth getting or downloading album of his)
Die to live is the most do-able vai song i've come across, it doesn't take too long depending on skill level to master the entire song,
for some awesome licks check out tender surrender off the same album
also - the animal has some quite easy(considering it's vai stuff) whole solo sections,
and of course for the love of god, which is probably the next entirely do-able song IMO
good luck