I bought Civ 4 and all it's expansions for £5 a few months back, played it once or twice and then forgot about it. I started playing it again this week and I really don't get it... I don't know what I'm meant to be doing. For now all it seems to be is, Next turn, Next turn, Next turn, Next turn, Do recommended thing, Next turn, Next turn and so on and so forth. I would love to hear from some Civilization fans to hear what they had to say about everything and see if they could point me in the right direction.

At first I didn't get it either. I only spent 20 some odd hours into it and I haven't played it for a while. not cuz I don't like it, just things came up. I love the game and its really fun. Basically, I think, the point of the game is next turn. Build up a civilization in turns. Try to take over the globe and what not. I'm not the best person to describe the game to you, obviously. But yeah the point of the game is to build up a civilization over hundreds of years.

Whooo boy, here we go.  
 
Civ 4 (and most similar turn-based strategy/economic games) is mostly about exploration, expansion, conquering territory, or winning via fiscal means.  To hit the end game, you have to generally focus in on one of those things - personally, I find cultural and science victories to be the easiest, but there are an insane number of ways to play and win.  Each ruler comes with predetermined suggested tendencies, such as Exp (Exploration) or Rel (Religion).  These give you a clue as to how those rulers might play well in your particular scenario.  While those aren't exact and you can play the game any way you want to, think about them as general guidelines for each society. 
 
Yes, there are a lot of "end turns" without doing anything, but I never recommend automation in your units, which not only will help you as you develop cities with workers, but will allow you to keep better tabs on soldiers and help when going to war.  There's a lot to track, but once you've gotten a few games under your belt, you'll get it.

It really depends on how you play. Especially at the beginning of a game. You can either expand rapidly at the cost of leaving all of your bases defenceless and underdeveloped or you can have fewer cities but have them developed and strong against enemy attacks. How you do this depends on the resources, terrain and a little bit of luck really. It's all about getting the best pieces before the whole map is conquered. When the early phases of developing are finished it's about diplomacy. Form alliances and wage wars on your enemies, befriend everyone, or just kill 'em all and let God sort 'em out. Alternatively, develop your towns, research technology and build wonders to become the most cultured in the world. Eventually, you'll need the resources and money to build a space ship to get to Alpha Centauri. 
 
How you do all of this can greatly vary for everyone so it's a bit hard to tell you how to play. By the sound of it though it looks like you're letting the computer steer your game too much. Research the techs you want to get certain buildings, units and abilities and tailor them to your own playing style. Play either culturally or militarily.