In this recipe the proportions are not all that important, so you can vary them (a little more, a little less) according to your taste. If you are fond of garlic, for example, you can double the quantity indicated.
It's not absolutely necessary to roast the pine nuts, but I find that it gives the pesto a richer flavour.
If you don't have any pine nuts, you can use walnuts instead.
The basil which gives the green color tends to oxidize easily, and therefore lose this beautiful color. To keep it better, add, before blending, the vitamin c.