I have an interview but i need advice/help its my 30th in a year and i have failed each of them?

ive been unemployed since january of last year and had interview after interview i can say ive had 30 in the past year and failed them all but im coming to a end to a retail course called tng it was horrible to begin with but thats because they were understaffed and their system was slow but half way through say my 6th or 7th week i was offerd a placement for WH Smith to do every wednesday to friday i would say it has helped my confidence but i really want this job at linzi shoes i love that store but can anyone give me any advise if you no what im going to expect or how i can do better in the interview i will be ever so greatfull my interview is this thursday so i would love some advice ASAP lol thanks x