I learned Welsh at school — where should I start?

Most people in this position do not need more vocabulary. They need permission to speak imperfectly, and a small set of sentences they can rely on.

Start from what you can produce

Recognition is not production. Choose five sentences you can say without thinking, and use them until they feel automatic.

Do not start from the beginning of a textbook

Start from a situation instead: ordering, greeting, arranging to meet. It is faster and far less discouraging.