Sorry I didn't get back to you yesterday. Generally lazy on tppc nowadays tbh. Been asked about speed tower by someone else as well so just copying and posting my reply:
Hey man, there are quite a few things you'll have to try out for yourselves because it can get long if I try to cover eveything but here's a few things:
Since you want the XY pokemons you'll want a record between 39-42 in general even on weeks I don't play.
You need a Deoxys(attack) equipped with Elemental Stone, with the following moveset:
Iceball
Close Combat
Psychic
Ancient Power
The general rule is kill everything in 1 hit/Some weaker pokes in 2 hit or deoxies dies.
You'll need to consider a few things when fighting them but the biggest thing to keep in mind is that the 1st, 4th, 7th etc pokemon(every three) is the same level as your highest level pokemon, the 2nd, 5th, etc(every third pokemon) is 1.2x your level iirc, and the 3rd, 6th, etc is 1.5x your level. This continues until the 18th pokemon(1.5x your level) where the 19th poke is 1.8x your highest level and the 20th is 2x your highest level.
In general the 1st tier is easy to with ancient power and you use them as much as you can to set up ancient power, maybe use ancient power on some 2nd tier as well. Having ancient power helps you kill the 3rd tier along with the 19th and 20th pokemon with some luck.
Another thing to consider is to do it in the day when dark pokemons have -10 stats making them easier to kill. Again, perfect target for ancient power. The first six pokemon are normal, then every three pokemon switches between shiny and dark with the last 2 pokes being shiny.
Beyond that it would be very tiny details that goes on forever. I don't wanna type it all and tbh I can't think of everything off the top of my head. The best you can do once you have the basic strategy is to keep trying until you figure stuff out yourself. You'll see patterns, know what you can kill with what move etc. With some luck on the set you fight, the critical hits etc you'll get a decent score.
There are a few other pointers in here particularly on my own posts within the thread:
http://forums.tppc.info/showthread.php?t=594367
Not sure what else to say. Hope that helped a bit. Cheers.
As far as what you win, I'd ask you to refer to tppc wiki. GL mate.