I think the mandolin has helped me the most with the fiddle since they are tuned the same and fingered the same. A lot of times when I am learning a song I will pick it out on the mandolin and then transfer that knowledge to the fiddle. Guitar and fiddle are completely different and I just use my guitar for chording and an occasional finger picking song so that one doesn’t help me as much with the fiddle as the mandolin. It is a nice change though to be able to play around with other instruments. The guitar was the hardest on my fingers so that might be an issue in the beginning. Good luck to you and have a good time since that is what music is all about.