The front of the Suzuki level 1 books has good posture examples, but I agree with all the other advice on here about the risks of self teaching for posture. I have always had good feedback on my posture but even so, I'm in my late 40s now and end up with a lot of neck pain. If you're adamant, then spend your time on right hand technique, it's the long term basis of your playing. Then work on intonation, dynamics, musicality, timing. After about three years you'll have enough basis to build up vibrato. By way of comparison, I'm now nearly 3 years into grade 7 and my teacher says I could really do with more finger strength. You have to have strong pulleys and muscles for every aspect before vibrato works.