My main focus of study is on healing and curing magic, is there a way to practice spells without having an afflicted patient to test spells on? And if so how do I know if a spell would be successful when using it on someone who is sick or injured?
You can practice anything you like anytime you like. The more you work with magic the better you will get. I suggest studying more and look into healing herbs, stones, and which god/goddess associates with them. Believing what you do WILL work, rather than it might work. Know what you are doing and have faith that you can.