When you start a hobby such as parchment craft where the range of equipment required is quite large, it is often difficult to decide what to buy first. If you have seen a pattern you really want to try, it will have a list of special tools and equipment required for that pattern but there are essentials that you probably cannot do without.
For tracing: a white pencil, white Tinta ink and a mapping pen and a ruler
For embossing: a range of ball tools or shaders and a sun/star tool and an embossing mat.
For perforating: a single and twin needle tools and a thick perforating mat, scissors or snips
Colouring: I think I would go for a pack of pencil crayons first and a pencil sharpener of course
Don't forget that if you want to buy a grid make sure that your perforating tools are the same make. PCA tools fit PCA grids and Pergamano tools fit Pergamano grids.