Wa Alaikum Salam.
I would recommend to not go for them. Too much thin profile, like 50-55 will make your ride extremely uncomfortable and hard. Secondly, our roads, potholes, etc. do not allow to go for such thin profile tires. This much profile tires will get damaged quite early and easily, rims will also get damaged.
Yes! For rims. especially alloy ones, you will also have to take care of offset, etc.
I also own 2015 model, 1KR-FE, 1.0L, 1.0F Vitz, and going through the same thoughts.
Based on my working till date, I would recommend to go for Light weight, 100% genuine and original, Lenso rims. They start from 15". For details about Lenso rims, please visit following links:
https://www.lensowheel.co.th/
Their latest catalog for 2019: https://drive.google.com/file/d/1rzGkWbq8EwLf8PK8J6h1c1LXAwuq4gH1/view
Read their blogs especially! You will learn a lot!
(I just came to know about their blogs today): https://www.lensowheel.co.th/blog
Their official distributors in Pakistan:
PAKISTAN RUBBER & TYRE CO.,
Address: 79-C NATIONAL HIGHWAY PHASE-II EX-II DEFENCE OFFICERS HOUSING AUTHORITY KARACHI, PAKISTAN.
Phone: +92-21-3580-4646 to 51, +92 21 538 0888
Contact Name: MR. RASHID RAZA
(Source: https://www.lensowheel.co.th/dealer/search?zone=7&country=9&inter=true )
And this company is also the official importers / distributors of Yokohama Tires in Pakistan. For details about the company, please visit: http://www.prtc.net.pk/
In a nutshell, I would suggest to stick with max. 15" rims (avoid 16" / above rims), max. width 185 mm, max. profile 60-65 (avoid 55 and below). The tires coming in my mind at the moment, and meeting this criteria in 15" are:
175/65/R15
185/60/R15, and max.,
185/65/R15
Do not go above 185/65/R15 at any cost! (And for this, you may have to go for 0.5"-1" spacers / packing)
Tire brands which I will recommend:
Yokohama: Advan db, Bluearth series and A-Drive.
Bridgestone: Ecopia, or at max. Techno (as far as I have worked, Ecopia is not officially available. Only Techno is available with made in Indonesia).
Michelin: Energy XM2 or Energy Saver +
or Continental tires (CC5 or CC6, etc. series)
I hope. It all helps. Thank you.
(I have discussed a lot about tires, rims, and their many details in my main thread, and many respected members have also contributed. You can check it too).
I hope, it all helps. Thank you.