Get a compiler that can deal with objective-C and start programming. If you're stuck on windows, the MinGW port of GCC handles objective-c, so long as you remember to get the optional objective-c bits with it. If you can use Linux or mac OSX, it'll be easier.
What will you be coding on - Windows, Linux or Mac OSX? Or even something else?
I would start learning Swift as it is a relatively new language. If you have a mac you can download xcode and start coding if you are on windows you can use vmaware and run a torrent version of the software on vmware it s rather slow and not legal so it s always best to use a mac. If you need swift lessons let me know