No one is going to be able to give you proof, mainly because magick is not something you can see and it is often not instant, taking days, weeks, months or even longer to display a magickal response. Everyones experience with the practice is also very personal, each person having slightly different beliefs and paths.
Belief is something that you need to find within yourself, no one can give you belief in this topic other than reasuring words that, nearly everyone has a time during their practice or in their path where they doubt the reality of it all.
Taking a step back, reading some books on the topic or talking to some other practitioners can really help re-develop belief.
The proof is in the results. But even then, it can be equated to mere coincidence. The reason being magick is subtle and works within the natural laws of nature and physics. It's not like anime or Hollywood movies. It's often times things like subtly attracting money, love, success, and the like. But let's say you do a money spell and get a little extra scratch. Let's say your mom just gives you five bucks because she was feeling generous that day. Does that mean your spell worked? What you take to be proof is on you. Nobody can make you believe. That is your choice.