1 Celebi prime
2-2-2 Meganium prime
Pokemon Total = 31
2 Pokemon Collector
Trainer/Supporter Total = 11
6 psychic E
13 grass E
Energy Total = 21
A pokemon deck is only allowed to have 60 cards and you currently have 63, so we'll have to cut a few cards to make it tournament legal.
You have lots of great pokemon in your deck, but way too many of them. Reducing the pokemon you play will allow you to focus on certain strategies and give you the bench space to be able to do so. 1 cleffa should be sufficient in case you need a new hand. 1 celebi prime is great against decks that dont attack with just basic pokemon and allows you to have an extra energy attachment per turn. I like the muk since it drags up your opponents benched pokemon and inflicts special conditions on them. Then it deals extra damage with it's second attack if those conditions are still present. Increasing your number of roserade to be able to inflict conditions on the active without having to use muk first, could also be helpful (a line of 4-3). I would also increase the line of muk to 4-3 rather than 3-2. I would also consider adding in a line of leafeon which also does more damage when there are special conditions on the active (possibly 3-2 or 4-3). To make room for these, I would drop the tangrowth, serperior and meganium prime.
21 energy is way too much. When you attack rainbow energy to roserade, you'll be inflicting both conditions on your opponent, so I would add 4 of those. I'd increase your DCE to 3-4 as well since muk is your primary attacker. The remaining energy should focus mostly on psychic since leafeon only needs a colorless for it's ideal attack or a grass for the secondary attack. I'd recommend 5 psychic and 2 grass.
This part of the deck should contain almost half of your cards. It's not helpful to have great cards in your deck if you dont have enough resources to get to them. Early game you want a pokemon collector, so increasing the number in the deck to 3-4 (adding in dual ball if you don't have enough to meet this number) is ideal. You could also increase your pokemon communication to ensure that you can get what you need. Muk has a heavy retreat cost, so you'll want to add a few switch to get it out of the way in case your opponent uses pokemon catcher before it's ready. You'll also need 2-3 pokemon catcher of your own and 4 junk arm to reuse all of your trainers. Your deck is going to be a bit slow to set up, so the 2 twins is a great idea. You'll also want a flower shop for recovery later in the game.
The biggest part missing in this deck is draw/shuffle power to get what you need. Increasing your number of professor oaks new theory, adding in a juniper and a few cheren will solve this problem. You could also try running seeker to be able to reuse your roserade and rainbow energy to inflict more confusion (but be prepared with a roselia on the bench ready to evolve or another roserade ready to attach the rainbow to).
By reducing the types of pokemon you run, you'll be able to focus on a strategy - to inflict special conditions on your opponent and do more damage because of them. I hope my suggestions help!