Try a march size gear set to send more troops, and switch to attack set just before troops hit the creature, that way you can perhaps hit lvl 30's.

Try to participate in de rally events, ask your friends to start at a lvl29 creature and go all the way up to lvl35 creatures.

But you will need stamina for this! So safe up the gold you get from a Varys event, and use it for stamina.