Want to buy a portable charger for iphone which brand?

I want to buy a portable charger for I phine and don't know which brand should I go for which is reasonably priced.

The pretty much all should work, anything that is 3 to 4 times the capacity of the actual phone battery is always a good start. The 10000mAh plus range, is always good, that way you don't have to worry about charging either the phone or the charger if you forget one day. But be warned, some of the chargers may take a much longer time to fully charge than your phone or tablet.

As for reasonable price, only you know what your budget is, but for me I would not spend over $50 bucks for one. Amazon and eBay are great places to look for them. Stay with the major name brands. I like Anker, Power Bank by Asuka. Both companies have great customer service. And on Amazon, many of the chargers will have reduced pricing.

Things I look for when buying them for myself or as gifts:

At least 2 USB charging slots so I can charge more than one phone or tablet at a time.
Rated for charging iPads on at least one of the charging slots.
Smart Charging, so you do not have to worry about what you are plugging in, if it recognizes the device it will charge it without a problem and may even fast charge if the device allows for it.
Charger comes with it's own wall charging cord/plug.

Apple. Their chargers are not expensive. If you can afford the phone, you can afford the charger.