I would recommend Khan academy, but I don't think the resource is that important. What is important is consistency, if you grow by 1% every day for a year will

I would recommend Khan academy, but I don't think the resource is that important. What is important is consistency, if you grow by 1% every day for a year will be 37X where you started(1.01^365 =37). So do a little every single day and you will be fine. I find this to be better than to do something every week. It is easier to get in rhythm if you do it every day, you can find fifteen minutes every day, on your way to and from work, during lunch, heck you can even do it while you're in the bathroom. I always tell myself the Bruce Lee quote “Long-term consistency trumps short-term intensity.” Take your time and be consistent.