MTG Arena - Cat Lifegain (Standard)

The core card of this build is Ajani's Pridemate. Every time you gain life you may put a +1/+1 counter on it.
The rest of the build either tries tick life gain as often as possible to strengthen Ajani's Pridemate quickly or to protect them.

Leonin Vanguard, Diamond Mare, Inspiring Commander, and Aetherflux Reservoir all give 1 life if their condition is triggered. Note that all these effect trigger separably, so often times Ajani's Pridemate gets several counters per turn.

Inspiring Commander is also our card draw engine, as most of our deck are cheap creatures and every single creature card creates a creature with 2 or less power you are often able to cascade through your deck.
However it's very costly with 6 mana so I've been thinking about reducing the number to 3 or even 2.

Aetherflux Reservoir also gives us an I WIN button once our life exceeds 50.

I'm unsure about Regal Caracal; most cats in our deck already have life link, and +1/+1 rarely makes a difference for Ajani's Pridemate.
On the other hand the life gain of a powered up Ajani's Pridemate often puts you over 50 so you can use your I WIN button.
An alternative to it is Key to the City, as it allows your Ajani's Pridemate to attack the oppenent's life points directly.

Dauntless Bodyguard protects your Ajani's Pridemate from destroy effects, and Fairgrounds Warden clears the way of creatures you can't get past otherwise.

Ajani, Adversary of Tyrants is almost perfect for this build. His -2 can get more than half of our creatures back from the graveyard, most importantly Ajani's Pridemate. His -7 gives us an army of cats who are buffed by Regal Caracal and trigger Inspiring Commander. Be careful not to lose by drawing too many cards, though. His +1 is often best spend on creatures like Leonin Vanguard or Inspiring Commander to make them harder to kill.

You can properly get by with a couple less Plains, and thus add more cards from the Sideboard or Maybeboard into the deck.

Note that the side deck is still under construction.