Little tips.
Baa bar is a great little place at your age. Pound shots they make up is fantastic, although when i was your age (lol) they made them up on the spot so there was one with sambuca and vodka and stuff we used to get. But it will be busy so go early for the shots.
Krazyhouse- Avoid like the plague. I used to go there when i was younger and was great, but now it is run downhill faster than a cheese in yorkshire. Pay to get in, drinks are essentially 1.50 but you have to pay for two at the same time so not too bad. But you have to pay a pound EVERY time you want to go for a smoke and you need ID to get in because they scan it into a machine! So yeah, the place is a dive now.
Cava- tequilla shots £1, all different flavours. Good range of lagers as well.
Is mood still a place in town? really dont know! If so it might be your scene.
Matthew street- Actually decent round there, go there towards the arse end of the night so 1-2am and the place is full of bars still lively. theres all diffferent types as well and probably easy to pull down there.