Yea, overdriver 10 is solid but a bit overated. To be honest, it depends on your way of playing. If you are competitive and aggressive, revoker 10 and storm rack 10 are better and stronger. If you play from the back mostly, you can get Pod gun10 or Graviton beam10. But the issue is that you can buy these 10-energy weapons, ou only have one copy. Personally in your situation, I would get Fragment gun8 to get two copies immediately, or get the fragment 8+12 if I have a strong enough mech. If you can wait a bit, the best weapon to get is Pod gun8 at 812k, cause you get a great weapon that allows you to stay back and you get two copies. Good luck, Hujik

Grav 10s n dual are your best bet for panther

Storm 10 pretty decent with epic radius n reload

Revoker 10 is pretty obvious close range. Get if you have surge. 

Overdriver I haven't tested but it should work well on a rank aegis paired with a 8

if you rank up once, you get 2. which is great for panther.