Any P. Cebensis strain will be easy to grow for a beginner.
if your next question is "what is the best P. Cubensis strain" the answer is there is no best. They are all pretty much the same, some just being slightly more visual than others. A reasonable comparison would be comparing two different strain of mushrooms that are not from the same species.
To answer the other question, grow kits are a waste of money and they take the fun out of growing. Your mushrooms probably won't be anymore potent, they may be slightly faster in growing, and the amount you can grow is limited to the space of your fruiting chamber (which in grow kits is pretty damn small) so your yield will probably be lower.
Stick to jars, learn some good techniques, have fun and safe tripping.