B-Vitamins (Please advise me)

After recently joining the gym I constantly felt tired. I know that B vitamins can help you release energy from food such as carbohydrates so I thought it might be a good idea to invest in some

I took a trip to the grocery store to find they only stocked B6.

I know there are other B Vitamins.

I'm just looking for advice on what each B-Vitamin does (mainly in relation to releasing energy from food)

And what is a good all round B vitamin supplement (Please note I am based in the UK and only really have access to high street super markets, but I will appreciate any advice)