Start when you feel like it. Crafting can be very overwhelming and it will take a lot of time to get anywhere, especially if you are just starting out and therefore have neither money not seals nor leveled retainers to speed up the process.

People talk about crafting gear for the class you are leveling, but tbh the best gear comes from dungeons and later on raids and tome trade-ins, so unless you are hellbent on never entering any content more than once, crafting or buying any gear while leveling up is likely not needed.

If you enjoy it though, there is no reason to wait and not get started right away.