To be honest, I'm not sure how much Stormont can do overall; large chunks of our budget have already been taken from the block grant to cover Bedroom Tax mitigations, and every NI government department's budget has been gutted in 2022 to shift more money to HSCNI.
The real issues, such as lowering fuel duty and imposing windfall taxes on energy companies, are not devolved, and Richi Rishi is too busy imposing ideological austerity and increasing tax burdens. In comparison, RoI managed to reduce fuel duty by 17p per litre, whereas Richi simply stated, "the best I can do is 5p." Bonus points for my tax increasing while inflation is at 8%.
The only thing I believe you can do in Northern Ireland is vote for someone other than the DUP in Westminster elections, who I'm sure would gladly enter into another confidence and supply agreement with the Tories.
Here is a comparison guide about cost of living in Ireland.