Non-target undergrad + target master’s advice

Hi, I’m about to start my bachelor’s degree in economics at non-target uni. I’m aware that the odds are very much against me but I wanna start as soon as possible to improve my chances at breaking into the field. I had very strong GCSEs but my A-Levels were weak due to a surgery which left me in the hospital for months. Ultimately, this is why I ended up at a non-target uni however I’m more than confident of my academic ability and work ethic. I know that I can achieve a first-class and I’m interested in applying for a master’s at a target uni down the line. I haven’t really been able to find much on non-target uni + target master’s students. I’d like to know if this is a feasible pipeline for breaking into the field. Moreover, I’d just like all the advice you guys can give me regarding strengthening application, connecting, interviews, etc. 

p.s. sorry if that was a little hard to read, I’m about to head to bed