The best place, like any other language you learn, is to start with the basic alphabet. Learning the signs for individual letters helps you finger-spell words if you happen to forget them later on (it happens to everyone, believe me!) or at least compensate for signs if you haven’t learned them yet.
In case J and Z were unclear, I’ve included gifs for you below (please excuse the lack of gloves or make-up; while I’m working on fixing the lighting of my apartment, I wanted to make sure my gestures were clear).
You take your letter “i” and bring it down before curving it up slightly like a hook.
It’s literally like making the pattern for the letter Z like you do on paper when you right it, only just in the air and with your index finger pointing outward.
I recommend practicing the alphabet slow at first; don’t worry about your speed when you’re learning sign language. If you try and go fast right off the bat, you’re going to mess up a lot and you may get frustrated at yourself more than you need to (trust me, it took me a long time to get as fast as I am now).
Practice the alphabet a few times a day to start with.
Like any other language, sign language requires repetition, but in a much different way. If you go from, say, English to Italian, you’re translating words in your head and associating different meanings with different vowel sounds and the like. Since sign language is basically just English (or any other respective vernacular) but with your hands, what you’re really doing is learning certain muscle controls and motions that take the form of non-verbal communication (instead of verbally speaking, you’re using your hands to “talk” for you, and you must train your hands to certain motions and movements in order to communicate efficiently).
If you have any questions, please don’t hesitate to message me!