First thing you should do/could do is decide on a federation and cat. (figure/model/bb/bikini whatever) - an experienced trainer and help you to decide based on the look you have, the time you will be able to put into it and your desried outcome (to place, have fun, experience)...once that is decided upon start looking at that federations site (the FAP rewards a soft look, NPC, harder and leaner, FAME a different look altogether). Your goal is to spend as little money travelling as possible since shows can be $$$$. UNLESS you want to go to a big one.
Ok, so based on the show, where you are currently and your goals and resources/ability you can now pick a date to compete....ideally you want to give yourself more time than you think you need esp for your first show.....now, I would suggest maybe getting some guidance on your diet and workout to bring you in where you need to be (online coaches are avail. You need not spend money on regular training provided you feel confident in the gym). A program and plan can go along way. Now work! lol, and once you have your schedule planned out, start to research/buy your suit(s), tanning, and all those neccessary things
Good luck