I'm a bit late to this thread, but if any other beginners are reading this, here you go I suppose.
My tips personally: - Learn full-alt from the beginning. - use a dk kd keyboard pattern - Don't put your hands in an uncomfortable position - and then just... play. People can give tips and "guides" on how to get better, but there's really no true "guide" to get better if you know what I mean? You have to find what works for you. The standard "Play More" really fits anywhere honestly. Push yourself. Don't just play maps that are easy for you. Play maps that are a bit harder. Take a break if your hands get tired or are in pain, because continuing at that point really isn't going to help you. Don't focus on the PP, the ranks, or the ratings for now; just continue to play and build up your muscle memory. A lot of taiko is about muscle memory.
There's not much else to say, really. This game is about playing more and you'll get better. Soon you'll be able to do patterns you weren't able to do before, be able to stream faster than you were able to before, etc.