The advice given by hitmonlee22 and Ivy_Profen is great, but I'm going to chip in my two cents because you dropped by the TCG Help.
Your deck looks a bit clunky. I feel like it would lack consistency when it is played, so let's see if we can fix that up with an improved draw engine. Secondly, I think the deck needs to be focused a little more on Meganium's Overgrow Ability. You ideally want to be tanking Meganium so it is 2-hit KO'd, and whenever it is attacked, its HP drops to 50 or less. I'd expect that in 2017 format the average damage output would be similar to that of these past few rotations, at around 170 or 180 damage per turn, or two turns of 90 damage. This is the "magic number", as it 1-hit KOs (or 2-hit KOs) the majority of Pokemon in the game. As such, we want to be able to survive the magic number with a little HP to spare, so we can use Overgrow effectively.
So, here's my recommendations:
-3-2-2 Ludicolo PRC (While at face value these look like really effective cards, they are far less superior to just two copies of Lysandre. This is because Ludicolo is clunky, takes up space and requires two turns to evolve, and then there is only a 50% chance of it working. If we include 2 Lysandre instead of this line (the ideal number in many decks), we have made room for 5 more cards. Also, Ludicolo's attack is hopeless, so we can replace it with some stronger Pokemon.)
-1 Remoraid (Making some space. You don't need 3.)
-2 Energy Retrieval (I don't think you need this many. The 8 Grass Energy is (surprisingly) a lot. I'm also suggesting Exp. Share, so with that inclusion you should need Energy Retrieval much less.)
- 2 Rare Candy (The Forest of Giant Plants Stadium is a superior choice, as we can get our Meganium into play within a single turn! The Stadium makes a large count of this a bit redundant, so let's use this space a bit better.)
-2 Wally (Same deal as for Rare Candy. The Forest of Giant Plants Stadium is virtually Wally on steroids.
)
-1 Steven (You can only use one Supporter per turn, so you must always make sure using your Supporter is worth the turn's slot. Steven unfortunately is not all too great, as we can use other Supporters to reliably draw into the cards you need instead.)
- 2 Professor's Letter (You've got a lot of Energy already, and with my Supporter suggestions and Octillery,you will be able to consistently draw into the Energy. Thus, I think we can use this space a bit better.)
- 2 Tierno (Tierno is not as good as a few other supporters (Sycamore and N). Tierno is only efficient in the right decks, and unfortunately this deck is not one of those.)
- 1 Pokemon Fan Club (Replace this with Bridgette. You don't have any EXs at the moment, so this card is better.)
- 3 Grass Energy (With the right draw, you won't really need this much Energy.)
-2 Double Colorless Energy (We have no use for this in this deck. Using DCE makes you a target for Enhanced Hammers and Jirachi Promos.)
+2 Sceptile-EX AOR or Virizion AOR (If you can get ahold of Sceptile-EX from Ancient Origins, than it would be a really good secondary attacker. It has a cheap attack that has nice synergy with Ariados. Otherwise, Virizion AOR is a pretty solid basic non-EX [G] attacker good if you fall behind in the prize trade, however it isn't all too great if you're ahead. Hence why Sceptile is much,much better.)
+2 Professor Sycamore (This is a great Supporter. So great, that we want four copies of it so we virtually always have the opportunity to use it, with the help of VS Seeker. You want to be using this Supporter quite often early on.)
+2 N (This Supporter is also great, but we don't need as many as Sycamore. N is useful for shuffling away hands that you really don't want to discard, as well as disrupting your opponent, especially when they're on less prizes.)
+2 VS Seeker (VS Seeker is an amazing and versatile card that lets you reuse many Supporters. Definitely a four-copy inclusion.)
+1 Lysandre (A bit of consistency. This isn't a necessary inclusion, however, but this consistency is really good for those clutch situations.)
+1 Teammates (Despite all our efforts, we're going to faint a lot. Teammates is great for non-EX decks in particular, so they can recover after being KO'd easier. With VS Seeker, we'll have access to this card for most of the game, even with just one copy.)
+1 Ultra Ball (Consistency.)
+3 Level Ball (This allows us to search for virtually all Pokemon in our deck for free. Running this alongside of Ultra Ball gives us much needed consistency.)
+2 Assault Vest (If our opponent runs Special Energy, we will be able to tank a bit easier.)
+3 Exp. Share (An issue with Stage decks, and especially this one with the higher energy-costs, is that they have difficulty streaming. With Exp. Share, this makes the streaming task a little less daunting.)
+1 Bridgette (To replace Fan Club.)
+3 Forest of Giant Plants (To evolve much, much quicker.)
+2 Training Center (This will allow us to tank better. While Forest of Giant Plants is more vital early game, this Stadium is better when we have set up.)
+2 Revitalizer (If we discard our Pokemon via Sycamore or Ultra Ball, or they simply get KO'd, we still have a nice way to get them back.)
Some good options, but I haven't recommended them due to space:
- A second Bridgette (Bridgette is a nice card to have Turn 1, so two copies boosts that chance.)
- A Skyla (Is a nice Jack-of-all-Trades type of card so you can complete a combo.
- Bunnelby AT (So you can get back a few cards late game that you really need. I'm thinking of Stadiums mostly.)
- A few Max Elixir and some extra [G] Energy (This would be nice for streaming, but I have absolutely no idea how to find space for this. You'd need space for about 5.
)
- 1/2 copies of Float Stone/Switch/Escape Rope (If any of your Pokemon are Lysandre'd (especially your high retreat ones), you have these cards as a bit of a safety net.)
- and lastly, Mega Sceptile-EX:
M Sceptile-EX is a different way to look at your deck. Both M Sceptile-EX and Meganium are tanks, which means they work together nicely. M Sceptile-EX is
really good for its Energy acceleration and it heals nicely, so it'll make streaming much better! Taking this approach would take a bit of focus off Meganium (which is not necessarily bad). This approach requires 3-3 M Sceptile-EX and 3 Spirit Links. You'd need to add some extra [G] Energy (bring it back to 11), keep the Energy Retrieval and add a fourth Ultra Ball. Assuming you go by all my suggestions (which is probably not likely =P), to make space I would recommend taking out the Ariados line (if you are looking for defensive over aggressive) OR Training Center (if aggressive over defensive), the Exp Shares, Level Ball, 1 Chikorita, Bayleef and Meganium, and a Rare Candy.
Anyways, I hope you find this feedback at least remotely helpful! =D