When your border are ready and the Spring is coming around it is time to buy your first annual plants. For us the Dutch it is very easy to buy annuals, they are for sale on every corner of street, any kind of shops they all have the annual plants. For the best quality plants to go to see the same people were you buy the best quality tools. A plant is not a plant, for the best quality you pay a higher price, it will give you more bloom and colour in your borders!
In Holland people do use mulch on the top of the border, but our climate gives us the choice, it is not always needed. People who use mulch should have less weed in the borders, moisture stays better in the border but there is also enough to write about borders without mulch. It's up to you.