First of all you need to fix your budget that in what pric range you want to buy a phone.Remember to keep flexiblity of 1 2k before fixing budget.My personal advice is to use a cheaper first hand phone than buying expensive but 2nd handed phone.Concentrate more on internal feature like ram and memory because the cosmetic features will be useless in long run.If you have good budget then ofcourse iphone is the great choice, I do not prefer samsung phone.In middle range one plus is nice choice.Redmi and oppo are good for budget range.Now everyone is coming with 4g volte technology so make sure your phone support volte.