Now, if any of my suggestions stop your team from being RU, just let me know. There are so many RUs running around that I'm having to give suggestions by the one I know best. By the way, this is a good looking first team and should perform well as is.
Ferroseed: I don't know how well this guy works in your experience. I'm just going with what happens with me. And that is that Spikes almost never works out. You spend all that time setting up, only to have some Rapid Spinner come in and get rid of three turns worth of work. Stealth Rock is just better in my experience, and this would allow you to give Uxie something else to help you out. Ferroseed is also easy pickings for Taunt, so you might even want to get rid of this guy for something else. Rhydon is a favorite lead of mine. If your opponent leads with a Pokemon you know has Taunt, instead of using Stealth Rock you can just hit them hard and take them down.
Rhydon (M) @ Eviolite
Trait: Rock Head
EVs: 96 HP / 92 Atk / 96 Def / 224 SDef
Careful Nature (+SDef, -SAtk)
- Stealth Rock
- Rock Blast
- Fire Punch
- Earthquake/Aqua Tail
Medicham: Medicham is looking good. Although it is probably going to be low on health really soon with Life Orb and Hi Jump Kick (mainly Life Orb). If you choose to replace Uxie with Hypno, you could get some nice Wish support to help with that. After all, you don't want to be easy pickings for priority or KO yourself before you've finished all you've wanted to do.
Ambipom: Try this set out.
Ambipom (M) @ Normal Gem
Trait: Technician
EVs: 4 HP / 252 Atk / 252 Spd
Adamant Nature (+Atk, -SAtk)
- Fake Out
- Acrobatics
- U-turn
- Low Sweep
Raichu: I prefer Pikachu with Light Ball over Raichu. After all, it isn't like Raichu is going to survive many more hits than Pikachu. Both are pretty frail. Speaking of which, if you do choose to keep Raichu, I'd take those Sp Def EVs off for either Sp Attack or Attack. Those 64 Sp Def won't help you survive.
Uxie: If you want to add Wish support for your team, you could choose to go with Hypno. Wish, Recycle, and whatever two moves you think would help most. It might not be as powerful as Uxie, but it still has bulk. The Wish support is still the only real reason to put it on your team.
Riolu: If you are having problems with Ghost types on your team, you could replace Riolu and add something to deal with those Ghosts, such as Bisharp, Spiritomb, or Shiftry. Or, if you just get tired of Riolu's unreliability, you could try out this Steelix:
Steelix (M) @ Leftovers
Trait: Sturdy
EVs: 252 HP / 4 Def / 252 Spd
Jolly Nature (+Spd, -SAtk)
- Autotomize
- Dragon Tail
- Rest
- Sleep Talk
This Steelix switches your opponent out with Dragon Tail, which gets help from Sleep Talk in removing negative priority.