I’ve been playing drums since 5th grade, piano since 8th grade, and banjo since 2007. Banjo is definitely the most rewarding of the three, but I think playing both drums and piano sets a really good foundation for learning anything else. I learned a lot of music theory with piano and developed a pretty good sense of rhythm with the drums. The hardest part of learning instruments (in my opinion) is getting from one “level” to the next (like a video game, haha). Moving from sounding like a child (a complete beginner) to sounding like a decent player (novice) is one big transition. The transition I seem to have the most trouble with is moving past just being decent. I know all of these terms are completely subjective, but they are simply the way I evaluate my own playing. I would say I am still a novice at both piano and banjo, but I have moved past that in playing drums (only in the last two years though).
My best advice is to saturate yourself with that instrument. Get a tutor, buy books about it, find out how it’s made, listen to music with that instrument in it, or find a group of people interested in playing that instrument and/or jamming. Jamming is one of the best ways to get experience playing. I’m not going to lie – it was embarrassing at first but in the end it helped me a lot more than anything else I tried.