I liked your deck a lot and I bought it as my first modern deck, and I would like to make some suggestions. What about pride sovereign? It is powerful and makes kitties with lifelink. And esika's chariot?
It's really cool to know you're having fun with the deck! I'm sure you know by the price tag that this was meant to be extremely budget, hence the omission of
Esika's Chariot, which is a little expensive. You could try it yourself and see how it goes, but that mana cost of 4 might not be exactly what we're looking for as far as the highly aggressive strategy goes, since it doesn't have an immediate effect on the creatures you already have ready to attack like
Regal Caracal or
Cubwarden do to make up for their higher costs.
As far as
Pride Sovereign goes, it was both a couple dollars above what I wanted to pay and a tiny little bit slow. It might be a reliable body, but when we're looking to win on turn 5 every game, we basically ignore the exert ability. It isn't bad at all, but we'll only get half the use out of it. It's probably a great idea for a card to swap out with one of the budget options like
Huntmaster Liger if you're looking to upgrade, which I can see from your list that you are!
Great list by the way! It's cool seeing people take an idea and run with it. I hope you have fun with your deck and have a great day!