I would recommend at least a full 4 ch set. Any extra equip can be used in the next plane. I think the extra cost will be minimal and why have to buy a 4 ch set in the near future or even another servo. You could always wait and get the fourth servo later as cheap as they are, your option there. You can order/pick up the servo when you order/pick up the next plane.

Nothing worse than an underpowered plane so I would go with something in the .19 area and just throttle back. Plus this engine will be more likely useful in a future plan

If you get a computer radio like cwrr5 recommended then for later planes all you would need to buy is the flight packs which would save money