What was your first plane? What charger/batteries do you have from that plane?

What radio do you have now? I don't know what plug in thing you are talking about for micro servos, but all except the very smallest servos (which that plane doesn't need) use basically the same standard plug. Any micro servo should do, an E-flite S75 or Hitec HS-55 should do fine and are around $10-15 each.

If you are going to use the included brushed motor the speed control should be fairly cheap. All you need is a basic, brushed ESC.

For size and weight you will be best off with a Li-po pack around 500-800 mAh. I had almost that exact plane and I flew it outside and liked the extra flight time so I flew it with 800 mAh and 910 mAh batteries. A bit heavier than it recommends, but I wasn't going for extreme 3D so it worked fine for me. However, I didn't use the included motor, so I can't say for sure what is best for a balance of run-time and weight with the included motor.