I am playing sapphire version, but that doesn't really matter at the part that i am having problems at. My team consists of 3 pokemon at the moment...

Marshtomp, lvl 28,
holding: quickclaw
Tackle
Mud Shot
Mud-Slap
Water Gun

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Kadabra, lvl 28
not holding anything
Confusion
Recover
Disable
Psybeam

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Ralts, lvl 19
not holding anything
Growl
Confusion
Double Team
Teleport

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I know my team is very unbalanced and the weakness is obviously dark pokemon (I got annhilated by Mightyena.). i was wondering what a good addition to my team would be or a good TM would be to give to a poke (one that i would have so far) . Thank you for your help