^if you buy only screenguards, cases and covers i dont think that going to china will be worth it. Because:
1. They are available cheaply here and not many people care about the quality and lots of the consumers are still after VFM. In this case the profit margin may not turn up like you expected. Also there are thousands of smartphones out there. For which models will you buy the accessories for?
2. You may not be able to sell all of your wares if you get them in large quantities. Phones get phased out very quickly. In this case your best choice may indeed be to go with wholeselling but that will further lower your profit margin.
3. Go to karol bagh and talk with the big guys. Ignore the small dealers, they cant and wont help you.
However you may consider personally going there to check the quality of the electronic items like charger, power bank and battery. No one likes poor quality electrical items. If you price them appropriately or competitively to the "Originals" then you'll get buyers.
Re-branding is easy. You just need to register your company.
I'll be happy to be proven wrong by anyone who has an actual experience in this.