Q.What Is The Best Potting Compost For Fuchsias?
Some hardy plants will be grown in ceramic pots and some in borders, when established. Others will be for next year’s Nguni baskets.

Certified GKH Gardening Expert
I would not plant directly into compost. I would mix compost with potting soil. Here is an article that will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/planting-in-pure-compost.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/compost-as-soil-amendment.htm
https://www.gardeningknowhow.com/ornamental/flowers/fuchsia/growing-fuchsia-flower.htm