New to the game! Would like some opinions on how to make my deck better!

I’ve been a really big of Pokémon since I was little kid but growing never had the opportunity to really invest in the cards until recently with that being said I’ve been playing ptcgl for about two months now and I’m having a lot of trouble winning matches ones I start climbing the ladder! Any advice or suggestions on how to make my deck stronger would be great I’m very much open to critiques!