Just one question, what level should my Pokemon be for the elite four...

It's good enogh to win but if you want it easyier level up to 55 atleast and get a few ice move otherwise you will lose to the dragons.

Your Pokemon should be on the late 50s, early 60s and I think training Bagon is a good idea.

These are good. Get your Bagon to a Salamence at level 50. (Shelgon evolves then). And get the reset to level 50. On blaziken get rid of ember with flamethrower or fire blast. The rest are good.
Hope this helps

You should try and if you lose just keep training.

Pretty much ok for a starter, just replace some of your move set's and level them up to 65-70 and your fine.

Wo,wo,wo,wo!!!!!!!! Ull have to boost them up about another 10 levels to be ready for the elite 4!!!!! They have like level 50 somethin'pokemon and they have they have good move combinations!!!!!!!!!!!

With what Pokemon you have and their moves, I would say you'll get wiped out. You have one fighting move & no bug moves at all for Sidney(Lvls 46-49) and he'd slaughter Kadabra. Almost no Ghost moves-just Shadow Ball & no Dark ones for Phoebe's Ghosts(Lvls 48-51)-you need a dark type w/a couple of dark moves, at least at lower levels. Hopefully your Electric will be enough for Glacia(Lvls 50-53), but keep Swellow out of that battle. Drake (Lvls 52-55)you have nothing to use really that's effective-either Dragon or Ice moves, but not on Dragon or Ice Pokemon as they're weak, so I dunno what to tell you there. Wallace's watery team (Lvls 55-58) is best beaten with Electric and Grass moves, but you can use Swellows Flying moves against Ludicolo, Tentacruel I'd attack with Psychic, and Milotic with WElectric, but it's tough. Whiscash is most vulnerable to Grass, and Electric won't work at all.
So, you need to fill in some moves, dump Linoone as he's just a HM slave with a couple of so-so Normal moves that won't help much(actually Surf is his best move though!). Swellow is sort of useless for the E4, too, and while Blaziken is good, Ember is worthless-replace it with Brick Break as you need the Fighting moves, Slash could go for a really powerful move of your choice or Flamethrower, but you could use that to replace Blaze Kick instead and use something else for Slash. You need to pick up a few Pokemon with better types and moves-like a grass/water/ice/dark Pokemon. Salamence would be OK, but you'd need to figure his moves to fit in with what you need, that may mean more replacements or tough moves to get, plus he's going to hurt against Drake's dragons.
I'd train up to 60 minimum, higher is better though, and give them all some items like Shell Bells to get HP back, or items to make moves stronger like a Magnet for Manectric or Twisted Spoon for Kadabra(can you trade him with someone so he'll become Alakazam, his stats should go up a lot) or a Black Belt for Blaziken's fighting moves. Plus, bring plenty of potions, heals, revives, ethers/exilirs, stuff like that, but train them up at least to level 60 first, or the more important ones!