Knowles Tree Service in N. Hampton. As someone mentioned above do a mix of “super loam” (better than just “loam” much cleaner) and compost. They should have both. If no compost there, lots of landscaping outlets offer bagged compost and anybody there could help you pick a good one. You will not need a lot of compost, use super loam for 90%+ of your base. Mix in 1-2 bags of compost per bed. (7yrs of landscape experience)