You don't specify what you mean by "small". One man's small amount can be a fortune to someone else.
If you've only the one source of income, you'll be restricted to putting away more AVCs into the existing AVC scheme or setting up an AVC PRSA of your own choosing. Check out the charges and fund options on both before making your choice.
If you buy shares yourself, you won't get any tax relief on the money you use to do so, which is a disadvantage this has over pensions. But you'll have access to the money whenever you like.