It would be helpful if you revealed what type of application you are interested in. Whatever the manufacturer recommends, try to double it, (this applies to glow planes only).

YNOT is right again. The 'most you can afford' is just about the best answer, given the information provided.

When you get into larger planes, this is still true, but the choices are simple...JR8711 or Futaba 9156. There is also the HiTec 9155, I think.

Speed and power are at a premium in 3D flying. That leads, inevitably, to higher cost (dammit). Do yourself a big favor and buy the best stuff you can afford. I wasted hundreds of dollars in an effort to save about a hundred dollars on servos, (and that was just one plane). It's just not worth it.

Listen to those who fly so much better than you it makes you want to pee. Don't listen to the 'experienced' guys who still can't fly after 30 years.

3D requires LOTS of servo power, get more than you 'need'. Period.