Before getting into Blood Magic (BM) you need to have a few things in place:
The above items will help you get started. The deeper you dive into BM, the more resources you will need.
BM is mostly based around a Tier system due to most of the progression being locked behind each tier of the Blood Altar. This guide will cover each tier and explain to you what tools/items/rituals/etc are available at each tier.
At the end of the guide, there are tables which will give you all the details about each Tier such as how much Will each gem will hold or how much LP a Blood Orb can Hold.