This deck needs better supportive options for Lapras and a lot less 1 ofs and less energy. I understand that you are a new player so it might be hard to get all the cards necessary for the changes I am suggesting, but try to get as much as you can, and for those that you can't I listed solid alternatives that will get the job done in their place. All of the changes are Expanded legal, which is usually the format I use for casual play cause unlimited is basically only about finding stupid loopholes to win instantly, so even casually I don't recommend it. Anyway, here are all the changes I would make:
Pokémon:
Note that some of the cards I suggest are somewhat expensive, so it is something that you will likely have to get over time. I would remove what is at the top first.
Remove (this will end up being most of what's currently in there):
Manaphy - Incredibly weak card. It's draw support is nice, but wasting an attack for it is almost always not worth it. A draw supporter like Sycamore or N are always better.
Altaria EX - Rather weak attacker, again many Pokémon that are more powerful or only give up 1 prize.
Gumshoos GX line - Rather average attacker. Many Pokémon you could get instead that are more powerful and are either basic or only give 1 prize card. Examples: Lugia EX, Huntail.
Bruxish - It's ability to ignore effects of attacks makes it cute as a tech to Jolteon / Glaceon wall deck, but I find it to be too weak to be worth it. Unless that is the only deck you ever face, I'd remove it.
Mega Blastoise EX - A bit torn on this one, it's a pretty good attacker (assuming you are using the XY/Evolutions one and not the Generations one) but it's so slow to set up, especially since you have no link for it. I'd personally remove it because I think the options I list below are better. If you decide to keep it however, I'd make it a bigger part of the plan by putting in a 2nd one and 2 spirit links.
Lugia / Articuno - Both are good cards, but I don't really like them as 1 ofs in this deck, I'd remove 1 (IMO Lugia) and replace it with a 2nd of the other. Or you could remove both if you find my alternatives more appealing.
Total removed: 7-9 cards
Options to add, #s in ()s are how many I would add:
3rd Lapras GX - He is your focal point, so you want to be able to get him out whenever possible.
Glaceon EX (2) - Incredibly good wall. Will give you some auto wins if your opponent has no basic attackers and doesn't run Pokémon Ranger.
Suicune (2 or 3) - Another solid wall. This one blocks EXs instead. In case you ever plan on participating in a Standard Format event, Regice is a weaker alternative.
Octillery (1-1 or 2-2 line) - Poor man's Shaymin. Gives you up to 5 cards every turn, but it's a stage 1.
Lugia EX (2 or 3) - Massive damage dealer. Enough said.
Palkia EX (3) - Energy acceleration is always good. I personally wouldn't run it because there are better alternatives IMO, but I thought I'd mention it.
Keldeo EX (3) - Combine him with a Float Stone and you have free retreat whenever you want (even if blocked by sleep/paralyzation or abilities or attacks) if he is on your bench thanks to his ability. This makes him awesome with Lapras GX as you can use him to cycle through Lapras so you can always attack. He also has a very powerful attack so he can actually get you prizes if need be. Standard alternative is Manaphy EX. Gives free retreat to any Pokémon with a water energy on it. Won't get around the blocks I mentioned before and can't really do much in terms of attacking, but free retreat is still a plus.
Huntail (2-2 or 3-3 line) - 20 damage for each energy on all your Pokemon for just 1 water is incredibly powerful. You can deal tons of damage and leave him to die while losing barely any energy. Also great because you can power up Keldeo and Huntail simultaneously.
In total I'd have about 10-14 Pokémon. I would personally run 3 Lapras GX, 2 Suicune, 3 Keldeo EX, and 3-3 Huntail for 14 Pokémon total. It gives a good mix so you should have an answer to any type of wall.
Trainers: 32
There are a lot of trainers that you are running that I think are weak so I will just list what I think you should run instead.
4 Dive Ball - At least how I suggested, you would have only water Pokémon, so Ultra Balls would be unnecessary. If you did decide to keep Lugia / Lugia EX (or don't have the dive Balls necessary) however, then you could run only Ultra Balls or a split.
3 Trainer's Mail - Really good at improving consistency of your deck. Alternative is running more of each trainer, particularly 1 or 2 ofs.
4 Max Elixir - IMO the better energy acceleration option. Works on everyone I suggested except Huntail, but he only needs 1 energy so it's highly unlikely you will need to Max Elixir him. Also Float Stone Keldeo makes it so you can Max Elixir your active. Alternative is Aqua Patch although it isn't out yet.
3 Float Stone - I'd recommend 1 for each Keldeo in your deck, but you might find an extra to be helpful since cycling Lapras is very important. No alternative to this, Keldeo needs this to be effective.
2 Fighting Fury Belt - Very good tool for bulking up Lapras and Suicune as well as giving a little bit extra damage. You can run more or less of these depending on how many basics you are running.
4 VS Seeker - Expensive, but they allow you to reuse supporters which is incredibly helpful. Alternative is running more of your supporters, particularly 1 or 2 ofs.
3 Rough Seas - Gives this deck some needed healing and you should always run a couple just to disrupt opponents own stadiums.
3 Sycamore - Best draw supporter in the game. Float Stone and Huntail are the only cards you are concerned about discarding. The rest you can get back or play before you Sycamore, so discarding your hand will almost never be a significant negative. Alternatives are more N / Kukui / Colress / Birch's
2 N - 2nd best draw supporter in the game as it disrupts your opponent's hand. Gets bad late game, but you have other draw supporters to fill that gap. Alternatives are more Sycamore / Kukui / Colress / Birch's
2 Kukui / Colress / Birch's Observations - This is personal preference. Kukui gives really weak draw, but it is good if you are often missing KOs by 20 HP. Colress is a very good draw supporter although it is awful early game. Birch's is a solid draw supporter. The coin flip can hurt you, but if it's heads it's a free Sycamore. Alternatives are more Sycamore / N
2 Lysandre - Very important for getting free kills on supportive Pokémon like Shaymin or on Pokémon the opponent is trying to protect to power/heal up. Also can be used as a stalling mechanism by forcing the opponent into a Pokémon they can't switch out of. Alternative is Pokémon Catcher, but I wouldn't recommend it as the coin flip hurts a lot.
Energy: 14
11-12 Water Energy
2-3 DCE
I personally don't like Splash as it hurts your Max Elixir chances, DCE is worth it though as it helps Suicune and Huntail a lot. Not very effective on Keldeo though. Anywhere from 12-15 Energy is good for this deck.
