"Shall I buy a vegan starter pack?"
There's no need to buy a vegan starter pack. Those are usually over priced, and what those types of packs contains, can be gotten typically at a lower cost individually, in the stores. The extra money you spend, would be better spent buying a bottle of five hundred micrograms (mcg) tablets, of vitamin B12.
I had correctly pointed out I'd accidently left out that I was referring specifically to vitamin B12. Which has been added to the existing answer.
However that five hundred microgram tablet, can be split in half, and you can get two worth days from. A sixty tablet bottle can actually cover four months worth of vitamin B12.