Hi! I am trying to get into battling with my pets and I spend exp to improve their stats but it still says im tier 1 how can I improve that?

Your tier is based off your total Strength, Health, Defense and Speed. [it does NOT include Intelligence or Level]

You will need your Total Strength + Health + Defense + Speed to be greater than 300 to reach tier 2.

There is a table with all the tiers on the in-depth guide

You can also see how far you are to the next tier when you are at the Spend Experience points page.

ooh I see ill go double check mine right now then! thank you so much

It's on the left hand side :).

You gain stats mostly by battling for experience points, using the training center and using stat boosting items on your pet.