Is my pokemon platinum team pretty good so far?

You'll want to switch Ponyta for Magby/Magmar or Houndour at some point, though that will be a little later in the game. Otherwise, species-wise at least, this is a pretty balanced team, though very heavily physically focused. If you aren't really attached to Luxio, grabbing Pichu/Pikachu keeps the same type while giving better access to special attacks. It may be worth grabbing Gastly, Budew, or Bronzor as a floating 6th pokemon to help you catch legendaries (Sleep Powder/Hypnosis).