Hey Akhayoon,
It's great you're starting to get some conversions. Currently however you still don't have quite enough data to make any decisions on just based on Manufacture alone.
How about breaking the data up even more?
Try ISP > PhoneType > Manufacture
Breaking up your campaign by ISP is the best way to know which carriers are doing the best. Phone Type just as it sounds will let you know which phone types are prominent ex. iPhone, Android, or other Smartphones. Finally breaking the campaign up by Manufacture to give you a little bit more detail on which actually working.
I see from the screenshot above that you have a few devices not performing very well. You could try to create new campaigns excluding these devices. Quite often however you'll find cutting individual devices will kill off your traffic, so be aware of that.
For now I would suggest you just keep collecting data and splicing your data various different ways to try and find whats working. If you could provide a screenshot of ISP > PhoneType > Manufacture that'll be a start. As well as any other variables you're tracking, such as categories, banners, etc.
-Brent