You have chosen a difficult color in today's environment. The dominant decks are Blaziken and Gardevoir decks and you are weak to those two specific colors and one of the tier-II decks (Aggron) has resistance to grass (I know Nidoking is fighting and that Gardevior is weak to grass).
It is possible to play two stage-2s, but very hard so I would advise that you drop one of them. I would keep the Sceptile and drop Nidoking, that will at least make your deck do well against the water decks that people will play trying to beat Blaziken. Playing 4/4/4 is OK, but I would change two the the Sceptiles to the non-holo version, energy trans is just too good to give up.
You then need to find some supporting Pokemon, ideally something that helps you against the fire decks. Wailord is a pretty good choice (not Wailord EX in this deck) because it can use the grass energy. You should finally add some SS Dunsparce to get your basics out and a Ditto (can be really useful with energy trans and wonderful against Rayquaza). Try a Pokemon setup like this
4 Treecko
4 Grovyle (you can choose to play some Rare Candy instead)
4 Sceptile (2 holo, 2 non-holo)
2 Wailmer
2 Wailord
4 Dunsparce (better than fanclub)
1 Ditto
You can try to find another good water Pokemon if you don't have Wailord, but the 120HP combined with the colorless attack makes it a good choice in this deck. You could also try to play two Suicune (energy trans gets past the power) and two Wobbuffet, that way be easier for you to get. Feel free to add other basics that have attacks that uses no more than one colored (non-grass) energy if you need them for the specific decks that are used in your area (Meditite can for example be useful against Aggron EX and Ampharos EX once you have enough damager on them).
You should then play something like 18 energies (14 grass, 4 Multi) which leaves you with 21 spots for trainers. You could change some of the grass to Rainbow if you go for the Suicune/Wobbuffet version (remember that Sceptile can move Rainbow and Multi Energy).
Mister Briney or Pokemon Nurse works well with Energy Trans but make sure that you have plenty of drawing trainers (at least 8 from Professor Oak's research, Copycat, Desert Shaman) and search (at least 4 from Oracle, Professor Elm's Training, Wally's Training). Switch or Warp points will be useful too, Rare Candy should be viewed as replacements for Grovyle. Stay away from the Balls and any healing cards other than Briney and Nurse.