You have awesome parts, man!
Well, first about the three combos you made...
None of those are good enough, considering the number of parts you have.
So, forget those.
Attack- Lightning L Drago BD145/CH120R2F might do you well in the tournament you are participating in. Most of us do not have top tier parts, so this may work well against us. Or even better, try getting Gravity Perseus before Sunday, and make Gravity Destroyer BD145MF. Its brilliant!
Defense- Basalt Bull BD145CS would have had been an AMAZING defense combo. Its a shame that you lost your CS.
But well, as you have no better tip for Defense, you must either drop out on Defense, or depend on anti-attack.
Stamina- Your Hell Kerbecs combo is great. The weird thing is, you are the fifth person complaining (to me; and make that six, as even I have been unable to beat an Earth combo with Hell Kerbecs) to not being able to beat an Earth combo with it.
At this stage, you may do one off these two things- Skip out on Stamina (which you mustn't, as you have nothing TOO good in the other two categories) OR try out something else.
A better combo to use would be a Basalt Kerbecs DF145EWD. It isn't entirely great, and to make it better, you again need a Gravity Perseus for its AD145.
This combo isn't better than Hell Kerbecs BD145EWD when considering pure Stamina, but with this, you get exceptional amounts of Defense. Most importantly, Basalt performs better than Hell in Stamina battles, because of the fact that it grinds away the opponent's spin speed.
As for adding MFs, it has been a highly debated issue. According to me, it doesn't affect a bey's Stamina to a large extent, and actually adds a lot of Defense!
So, your top priority at the moment should be to get a Gravity Perseus, so that you can make better combos.
EDIT- Beaten by a WHOOPING 7 minutes by Fantomu! XD
Team IB Revolutions
Thanks to N0body for the avatar and Synth for the signature!