At least you’re starting with an Si and not a DX. The most important thing you can do is come up with a plan, horsepower is NOT a bolt on affair, if you want to be successful you need to know what you want to accomplish before you get started and start spending money. That said probably the best way to get information on this is to join a Civic forum that focuses on performance mods and ask them what’s worked or what hasn’t, this way you’ll have a good idea of what you’re getting into before you get started and spend a bunch of money on parts that don’t work.