The first thing you do is get a new mag release. The one the gun comes with is plaastic and will become unreliable very quickly. New front optic front sight and you are ready to go. The sky is the limit basically, just depends on how much money you wish to put in the gun. The next edition for me would be a trigger job, smith and alexnader magwell, and tungsten guide rod to
add a little weight to the muzzle. If you want a bull barrel you can add it later. None of these really need to be done quickly except for the mag release, but out of the box you can go and compete with a para, just get a good gunsmith to go through it to make sure it is reliable. I also have 4 18rd sti tubes for sale for the para 40.