my advice is thus:
if you're not willing to/can't afford to by the books recommended, then you're at a bit of a disadvantage, you really do need to know a bit of theory on the subject unless you're naturally very outgoing or a bit of a thespian at heart.
I'm at a disadvantage all round really, I'm quiet, I don't have much interesting to say, and I've got butterthumbs instead of fingers. However, thrust a Rocky Raccoon, a set of sponge balls or a chop cup in front of me, and I'll have you rolling around the isles in no time.
Where did I learn my stage persona from? I learned it by watching other magicians, and studying what they did to entertain/make people laugh/captivate their audiences.
Firstly, let me ask you a question:
What do Criss Angel & David Blaine have in common?
Answer: neither of them have much of a personality, they mumble something like 'let me show you something' then they use whatever technical ability they have to astound you.
How do I know this? Because I've seen them on the telly. There's my recommendation to you - watch a LOT of telly. Have a look at TV Magic on
http://www.magicweek.co.uk and you'll see what's coming up over the next few weeks on TV.
Obviously, you don't want to be copying people or stealing their jokes - you have to be you, otherwise you're performance is going to be unconfortable and quite probably rubbish, but at the same time, you can learn a LOT from watching what other magicians do.
YouTube is another excellent source of free material. Search for famous magicians (you can find a list in the Magicians Hall of Fame section here), and watch what you can of their performances on YouTube.
You'll get stage grandure, presence etc. etc. from the likes of David Copperfield, you'll get comic timing from the likes of David Williamson, Bill Malone or any magician you personally find funny, and you'll get the true art of storytelling from the likes of Eugene Burger (not sure if he has any clips on YouTube though, but it's well worth a look).
My advice is therefore very simple. Consume as much magic as you can. There's a big difference between the major TV magicians - Blaine and Angel aren't going to be a huge amount of use, but you can learn a lot from the likes of Eugene Burger's performances and maybe Derren Brown or Max Maven, depending on what sort of thing you want to do.
What's also very handy is to look at some of the rubbish bedroom magicians peddling their nonsense on YouTube, some of the stuff is very funny for all the wrong reasons, but it teaches you how NOT to perform.
In the end, your journey is going to be one filled with trial and error until you find your feet, but I urge you to study other magicians (and not copy), learn what makes a good retort or why they pause in a particular place etc. and from there you will have a good grounding.
As others have said as well, it's a good idea to bring another interest into your magic, so you have some sort of passion in your performance. There's no good introducing a trick with a background history of ancient chinese warriors battling evil or something if you've no interest in history. If you like gambling, then work on some gambling routines. If you're interested in music, use music to your advantage, if you're into fast cars, then talk about sprockets or something. You get the idea.
When you've got a bit more money, then get the books others have listed, as you really need a bit of theory to properly crack it, and fully 'get' it.
Until then, a LOT of practise (and by that I mean actual performance), a lot of studying other magicians, and a lot of thinking carefully about what you're saying and why you're saying it is important. There's not really a short cut unless you're a natural showman unfortunately.