luke + R2D2 + swarm tactics
rookie Xwing x2
Gold Ywing + ion cannons
play is terribly simple. Use luke and always keep someone near him, preferbly aiming at the same target. Use swarm tactics to "rescue" low hp pilots, or rather use them one last time before they die. Ywing with ion cannon to help catch targets and guard Luke when using R2D2's repairs. 2 Xwing gives you a lot of tactical flexibility, and can do some pretty amazing stuff, especially if you have been playing the empire side for a while. Always try to go around in pairs, and you can feel free to split up if needed, into two groups. If luke kicks the bucket early, gather all 3 ships close together and hide within the Ywing's ion cannon range, then just pretend you are flying your usual 3 rebel ship formation. all 3 pilots at the same skill level helps prevents friendly overlap from occuring too much, so it is easier to maintain tight formations, and all 3 ships can plummet the same target together if they are close enough. try to keep both rookie Xwings close but away from each other, such that they are close enough to aim the same target at a reasonable range, while also being able to catch TIEs trying to range 1 the other Xwing. Ywing will help cover the butt of the other Xwing, so not too much worries as long as they stay close. Your only real issue is if your Ywing gets taken out, and you will lose some group cohesiveness and defense, as well as your tactical advantage, but if that happens, just switch back to your standard 3 ships play and go aggressive, since the Xwings no longer have a slow ally to worry about and can do their forward 4s happily.
Optimally, have the 3 rookies operate as a team, and Luke circling around the outside of the team and using swarm tactics on whoever happens to be close enough to benefit. Anytime he needs R2D2's repairing, fly straight into your group, and return any challenges to chase Luke with concentrated fire from all 3 ships. Alternatively, you could split them into 2 pairs, and have the 2 group operate independently on 2 seperate sides of the map, forcing the opponent to either split his group or send everybody against one pair, and thus allowing your other pair to pick off stragglers. 4 ships really helps you recover from unlucky situations, such as having 1 ship taken out early or getting disrupted by too many collisions. One interesting tip is using Ywing on swarm tactic to pick off low hp named pilots trying to escape or outside your normal firing arcs, by abusing the ion cannon's 360 range
I'm not happy with any of my current 3 ships setup at the moment for the rebels, so I really cant recommend any to you for the time being.