As the above poster said, there are no guarantees - there are certain things that you can do to improve your chances of getting a TC, but nothing that will guarantee it.
So to give yourself the best chances:
- get a good degree (which it sounds like you already have)
- get top grades in the GDL and LPC (obviously more important if you don’t have a TC when taking these courses)
- get LOTS of work experience (informal, vac schemes, CAB, court marshalling, perhaps some experince in a different jurisdiction etc)
- get lots of extra-curriculars to demonstrate teamwork etc…..
(If anyone else wants to add anything to the list please feel free, it isn’t intended to be exhaustive).
Whether or not the length of and stress involved in studying these courses is too much of a gamble is really an individual decision. Do you feel that you would be a strong candidate based on the above list, or do you need to do some CV building before starting the GDL? Obviously if you have a TC lined up before the GDL it is less of a gamble (unless you are unlucky enough to be one of the 45 disappointed potential Halliwells trainees). It’s up to you if you feel that you want it enough to warrant the time and stress.
Good luck! (and let us know what you decide!)