If you want to start painting and not sure what medium to use , the best answer would be is to try them all. Considering a high price tag on painting supplies, I would suggest starting with studios and workshops first. This way you can have plenty of experience with different mediums without investing in supplies. Look for studio in your area that will offer affordable classes and give you a freedom in making decision of what medium to use. I attended a studio for about 5 months and our teacher was amazing. She allowed us to work with different mediums and also to work on our own projects. To me, it felt like a private lesson every time. I explored paints, styles, tricks, techniques, and lined up my personal likes and dislikes about all subjects.
Browse the internet or search YouTube for painting techniques and discover your favourite artist. Visit their website to familiarize yourself with their work. Most of artists provide free video lessons that you can subscribe for. My suggestion is to subscribe for a few. It is very beneficial to observe different art techniques and styles. I also advise to follow lessons for one medium at the time, so you don’t get confused.
Once you tried a few mediums go ahead and start getting your very own supplies. Build your studio paint by paint!