The Olivine battle tower battles are really tough (especially levels 50~and up).

   You can't really do much with type-matching. But, even if you could, most of the pokemon have attacks that aren't the same as their type. You'll get an electric type busting out with ghost and fire moves! And even worse, the battlers here actually use their pokemon correctly (unlike the poorly programmed trainers you usually face) they also give their pokemon good items like 'Leftovers'. You should consider doing the same.

   Also, every single pokemon that I've faced in there so far -if they were able- had the deadly 'Earthquake' move. It's quite frustrating, expecially if you base your successes on levels instead of giving your pokemon good moves and boosting stats with items (both of these things you MUST do if you intend to win very much in the tower).

   Most all, switch out pokemon that have the 'Perish Song' cast on them... so you should bring along a pokemon with 'Mean Look'.

   Use your pokemon that have sneaky moves like 'Destiny Bond', 'Perish Song' (better yet, a 'Mean Look + Perish Song' combo) and the clever 'Substitute + Recover' combo (this combo will make your Mewtwo unstoppable!). Moves like 'Dream Eater' and 'Nighmare' work wonders if you can first put the pokemon your fighting to sleep.

   Since you only get to use three pokemon in the battles, make sure each of them is a different type! Don't over specialize. Always look for ways to include possible teamwork (use a certain move with one, and finish off with another).

   Bring a good solid electric type with strong moves like 'Thunder' or 'Thunder Punch', a strong ghost with some sneaky effective moves is a must, and an ice or psychic type with good stats. Fire and rock types are good too, but thus far in my 'study' of the tower, grass and bug type drop like flies (pun intended).

   Don't dare bring any water pokemon if they don't at least include 'Surf' in their selection of moves. Don't bring any flying types, they will go down in two seconds in the higher levels (on the other hand, a flyer is your only hope against an 'Earthquake' attack).

   Don't bother to bring your Chansy either, you'll get to heal all your pokemon in between battles and Chansy is no good in fights like these.