It depends on how customised you want your game to be. Programming things from scratch gives you full control, and you aren't relying on other people's programs (which may or may not work correctly nor do what you want them to do).
But using a ready made game engine or game creation tool can be easier if you aren't confident about programming.
In my experience, if I can't see how I'm going to make a program before I start, then I will probably get stuck somewhere down the line. I have to have a rough overall framework in my mind before starting, and flesh that out with finer details as I dive into it. I find it's best to aim for projects that are right on the cusp of what I know I can do. That optimises the chance of success, vs the sense of achievement vs the learning experience.
I have no idea how much programming experience you have, but given what I've said above, and given that you're asking for my advice on how to proceed, I'll say that perhaps a platform game is too challenging a project for you to program from scratch at the present time.
A game creation tool may be the way to go. Take a look here for two such tools: