Clematis 'Diamantina 'Growing clematis can be very easy if given the right location. Sun on the top, shade on the roots, and a nice trellis to grow. This plant is growing in my garden on the east side of my house. It gets about 6 hrs of sun in the morning ( afternoon shade) , its roots are shaded most of the day by a step going up to my deck, and the soil has been amended with compost.
Most clematis will perform better with regular pruning. Clematis that bloom during summer on new wood need pruning in winter or early spring, or they will look thin. Clematis that bloom in the spring on last year's wood do well if cut back lightly after they have finished flowering in the later spring or summer.
This cultivar is a classified as Group 2B clematis. It can be pruned in spring before new growth begins for a great flower display later in the summer or pruned after spring flowering for that the earlier show of larger, (but fewer) flowers.
I try to fertilize every few years. I may use Tomato fertilizer, rose food, or anything that has low nitrogen like 5-10-10.
If you are not lucky enough to have a sunny spot in your garden, no worry, there are several clematis that do well in part shade: Nelly Moser, Jackmanii, Alban Luxurians, and Silver Moon just to name a few.