Pkul85 are you now consistently eating a low glycaemic index, anti-inflammatory diet? When you can get some money together you would be wise to get blood tests rather than prioritising your skin; whilst your self-diagnosis is plausible you do not appear to have considered the possibility of a hormone imbalance such as PCOS or insulin resistance.
You have had good advice to try vitamin C (ascorbic acid or MAP), KinNiaNag and sunscreen. IMO you should consider switching from a chemical sunscreen to a physical one for a couple of reasons: firstly the chemical version needs to be applied to clean skin under your serum so it can be absorbed, whereas physical sunscreens can be applied on top of your serum protecting the actives from UV light and allowing them to fully penetrate, secondly chemical sunscreens can be irritant which is the last thing you need with PIH. AHAs can also trigger low grade inflammation than contrinutes to PIH. Since you are on a tight budget have you considered DIYing when you run out of the Avalon product? You can purchase kits that will make you several batches from SEA. The recipes were designed by one of SCT's 'mad scientists', DragoN, you will note this is based on published research to ensure the right concentration, pH and combination of actives are present for optimum absorption and efficacy. You can even DIY a zinc oxide sunscreen for cheap if you get the bug!