Hey!
First of all, it works better if you post your list here. Let me do it for you:
2x Dialga GX
2x Dusk Mane Necrozma GX
3x Magnemite (2 Searching Magnet at least)
1x Magneton
3x Magnezone
1x Tapu Lele GX
1x Oranguru (UP)
=12 Pokemon
3x Mt. Coronet
3x Guzma
3x Switch
3x Choice Band
3x Ultra Ball
3x Rare Candy
2x Fisherman
2x Pal Pad
2x Pokemon Fan Club
2x Professor Sycamore
2x N
2x Cynthia
2x Looker
1x Cyrus
=33 Trainers
12x Metal Energy
3x DCE
=15 Energy
Deck Theory:
Dialga and DM Necrozma are your two main hitters with Lele able to provide support when needed. Lele's Energy Drive attack is great for this deck if needed, because you are able to accelerate energy so quickly. Magnezone is your energy accelerator using Magnetic Circuit and even his Zap Cannon could prove useful in stressful situations against fairies. I mean, it can OHKO a Gardevoir GX, so... Plus, Magnemite's Searching Magnet let's you search out energy, 3 to be exact! Dialga's GX move is the only GX move you will want to use in this deck because you get another turn right away. Imagine OHKO'ing a Pokemon with Timeless GX (Dialga's GX), then starting your next turn, Guzma up a GX with damage and KO'ing that. 4 Prizes quick, with no way to counter because they have no turn in between your next turn. Oranguru works hand in hand with Looker, put any 3 cards on the bottom of your deck, then, if you do not get N'ed, use Looker to pull those cards you desperately need after you use Oranguru's Resource Management.
Now my reaction:
I think you're trying to build a Dusk Mane Necrozma / Magnezone deck with a few tweaks. However, I've got the following suggestions:
- 3 DCE (if you use Magnezone's ability it isn't really needed, and 12 metal energy is already quite much, most lists run 10 or 11)
- 1 Pal Pad (1 should be enough I guess)
- 2 Looker (I'm sorry, but it's just not good enough, replace it with 2 more Cynthia if you have them)
- 1 Dialga GX (besides the GX attack the card is not that good, 1 should be enough)
- 1 Choice Band (you're hitting 220 already, 250 with GX, in most cases that's already enough)
- 1 Fisherman (maybe - 2, since your stadium already does it)
- 1 Switch (normally I suggest 2 Float Stone, then - 3 Switch, + 2 Float stone, but maybe you don't have them / don't want to invest in Float stone's because they'll rotate?)
+ 1 Ultra Ball (you always should have 4 I guess)
+ 2 Cynthia (like mentioned above)
+ 1 Solgaleo Prism star (really good in this deck)
+ 1 Mt Coronet (Mt Coronet + Magnezone are the engine of your deck)
+ 2 Field Blower (it's great to be able to avoid ability lock a few turns against Garbodor)
+ 1 or 2 Professor's Letter (to get your energy out of your deck to fuel Magnezone)
+ 1 Rare candy (you need Magnezone, so use 4 Rare Candy for maximum consistency)
You also could switch Pokemon Fan Club to Brigette if you have those cards. And I'm not sure about Cyrus, but maybe it works.
Maybe there'll be more suggestions, but I think the above changes will already help you a lot and will improve your deck a lot!