If you are serious about calling in contests you will more than likely have to build your own calls or have someone build them for you. I built all my own when I was competing. I still build some for others that still call. It does take a lot of time.
I would watch video of not only turkeys but contests as well. Then video myself and try different calls till I got two that would be almost identical. That way you have a backup in case one goes sour while practicing.
Most of us use a specific call for each sound. The yelp requires one call the cutting and flydown another as well as the purr, kee kee and any other sound you may be asked to reproduce for the judges.
I would practice myself for up to 6 hours a day. Now that was building calls and watching video then doing the calls.
I would say rythym is a very big part of contests. Get a sound you like and can reproduce without errors and get your cadence down.
Good luck! There are alot of guys and girls that sound better than most birds!!!