The best way to learn calculus on your own is to free up some time and join a group.
i.e. the best way is to
not do it on your own, with limited free time.
To make good headway, you want a disciplined approach with someone to check your work. You'll want at least 1 hour each week ... formal courses usually have 3 contact hours a week and another two non-contact working on problem solving.
At that rate, it takes most people about a third to half a year to get proficient at 1st-year University level.
Still, you can start out by yourself. Since you are keen and sound inspired you should be able to cover the basics quite fast.
What level of education are you starting at?
What level are you aiming at?
You'll need some notes:
Paul's Notes are generally helpful with the ideas, there are also online
college courses that are very good ... but you also
need exercises.
Math is Fun pages try to be less serious about the whole thing. BUt if you are dedicated and rally don't have a lot of time, you can try one of the
crash courses people offer.
Note: calculus is normally taught alongside linear algebra.
You need to decide what you want to learn
for and how serious you are.
The courses online vary a lot so you will need to shop around to match the teachng style to your learning style.