Deck Building Help

Hello, I recently reached Infinite rank with an Agent Venom deck. However, the players at this rank have much stronger decks and are much better. I want to improve my Agent Venom deck, but I'm not sure what to do. I'll share an image of my current deck and the cards I own from Series 3.

I can also still choose a free Series 3 card, and I have 6,100 tokens, so I can purchase a Series 4 or Series 5 card. Also, I have 6 spotlight keys. Currently, I don't own any Series 4 cards and only have Agent Venom and Surtur from Series 5, as I started playing about a month ago.