I also think it'd be better if you continue from where the previous group left.
Unless you have an inhuman pace, new readers will end up reaching whatever you translated and go to another place to read the rest. It's better if you focus on the latest chapters, specially since most people are already up to them.
Or maybe you can strike a deal with another TL so he translates the new chapters while you fill the gap.
Anyway, good luck with that. You picked a popular series so you will get a lot of picky readers and fanboys of the previous group shitting on you but as long as they don't offer any useful criticisms, just let them screech in their corner.