Can anyone tell me the gym leaders and their Pokemon please?

Roxanne
Geodude lv14 - Rock and Groud type
Nosepass lv15 - Rock type

Brawly
Machop lv17 - fighting type
Makuhita lv 18- fighting type

Wattson
Magnemite lv22- electric and steel type
Voltorb lv20- electric
Magneton lv 23- electric and steel type

Flannery
Slugma lv 26- fire
Torkoal lv 28- fire
Slugma lv26- fire

Norman
Slaking lv28- normal
Vigoroth lv30- normal
Slaking lv31- normal

Winona
Swellow lv31- normal and flying
Pelipper lv 30 - water and flying
Skarmory lv32- steel and flying
Altaria lv33- dragon and flying

Liza and Tate
Lunatone lv42- rock and psychic
Solrock lv 42- rock and psychic

Wallace
Luvdisc lv40- water
Whiscash lv 42- water and ground
Sealeo lv40- ice and water
Seaking lv42- water
Milotic lv43- water

I think, for a starting team, you should choose Torchic (since it will be awhile before you can catch Fire pokemon). Catch a water Pokemon like Wingull, or use Beautifly to beat Roxanne. A Swellow or Taillow should make quick work of Brawley, and Combusken (Torchic evolved) can easily beat Wattson. Catch a Marill when you can to beat Flannery, and at this point, you should be far enough along to catch your own pokemon!

To sum it up I recommend these pokemon.
Taillow at Lv13 with Wing Attack and Quick Attack
Wingull at Lv13 with Wing Attack and Water Gun
Torchic at Lv16 ( which becomes Combusken) to learn Ember, Peck, and Double Kick.
Marill at Lv 10 at least, but learns Bubblebeam at 21 (must delay evolution)

The last two slots are up to you, but it might be a good idea to grab an electric Pokemon such as Electrike.

Hope I helped!

Look in a walkthrough for the Pokemon that the leaders have

A team for a beginner well I can't really because I know the best non legandarie Pokemon but you only get them late on in the game

Heres my team

Sceptile
Snorlax
Heracross
Latios
Regirock
Donphan

Hope I help