The wording is somewhat broken in two places. I assume you want to write:

• "where X is the number of lands sharing a land type with that land that you control"

and:

• replace "dealt that damage may be dealt" with "you may have this spell deal that damage"

In fact the wording for the exact thing you are proposing is a bit complex, but it also seems like this should use a reflexive trigger anyway, so the full text could be:

• "[Cosume]
  Search your library for a basic land card and put it onto the battlefield. It enters tapped unless this spell has consumed. When the land enters, this spell deals X damage to target creature, where X is the number of lands that share a land type with that land. If this spell has consumed, it deals that damage to any target instead."

Either way, that's a very wordy spell. I hope the set has plenty of dual lands or other nonbasic lands wit land types to reward tutoring for land types you already control - otherwise this spell would be wordy for little pay-off.

You're right. I also just realized I already did a similar and significantly better uncommon Worldfire Ignition and a common version Bounteous Violence of this card. I'm going for an entirely different design.