grow something you like, as you're more likely to take care of it!
some easy veggies to grow are radish and salads, which are nice and quick
potatoes are also quite easy if you don't mind a bit of digging
you could make life easier for yourself if you buy seedlings, partly grown plants or onion sets from your local nursery, cutting out some of the hard work and getting quicker results
if you are determined to make a success of it I am sure you will do ok - good luck!