Fiddle
To see yourself make progress, find time to practice a minimum of 30 minutes a day. Skipping days will impede development, and you’ll only regain the point at which you previously stopped. (Professional studio musicians practice 8 hrs.) If you can ever manage it, set aside a whole day when you can practice, the progress gained during extended sessions is greatly improved. There are summer music camps where you can attend classes for weekend, or week long periods, and achieve much more advancement than spreading the same amount of time across months.
This is stating the obvious, but always practice with your fiddle in tune. You’re training your ear to recognize accurate tones in conjunction with finger positions (intonation) so the tuning of the open strings is essential.
Instead of always trying to learn a tune completely from beginning to end, look for ways to break it into smaller parts. A smaller phrase practiced repeatedly in a loop gives your fingers and bowing a better chance to acquire muscle memory, then stringing together the smaller phrases becomes the whole tune. Repetiton is the key to learning.
When attempting to learn a new tune by ear, try singing, humming or whistling along with the melody first. This may be a natural talent you can draw upon that will bring you a step closer to learning by getting the music in your head. Eventually, the fiddle will be like another voice by which you can express what you are thinking aloud with fingers and bowing,
Keep a list of tunes you learn and the keys they are in. You might even care to pay attention to the original sources the tunes come from and details of where and when they were from. As a performer those details are useful to give more background to the show.
Find people to play with. There’s much to gain from having others to exchange music with while learning, and if you ever find you want to try performing in public it beats playing solo.