Just curious, why do you want to start at a LCC??? I'd never worked for an airline before, but went straight into BA. With these big carriers it's all about seniority, so the sooner you get in the quicker you become senior, and the quicker you'll get to long haul.
Anyway, in answer to your question, I'd say that customer service experience is probably one of the most valuable things you can have when applying to an airline, cause they always want examples of you dealing with customers etc.
I'm not sure what the recruitment process is for the LCC's cause I've only ever applied to QF and BA, but I would assume it would be much along the same lines...Group interview, pannel interview, medicals etc.
Hope this helps a bit!