I find TCL to be a very good brand. I suggest you take a look at the TCL S305 series, which costs around Rs 20,000 and is available in a 50-inch variant with 4GB RAM.
It also has Fire TV support inbuilt in it, which makes it very easy to stream content using your remote control. It has got an RMS of 10W per channel, which is decent enough for a TV. I would suggest you buy TCL S305 if your budget is around Rs 20,000.
Apart from TCL, we also have Xiaomi, which impresses us with their home appliances; they have recently launched the Mi TV 4A series in India.
Mi TV has a budget of 55-inch Android Smart TVs available for just Rs 26,999. This TV also comes with voice-control support, so you can control it via the included remote. The TV offers pretty good RAM and internal storage, which is enough for the OS and apps.
These are some of the good options which you can look for. Other good options include VU, which offers 4GB RAM with a range of TVs as well.
Also Check Best Selling TV Under 10,000, 20,000, 30,000, 40,000, 60,000, 70000, 80,000
Hope this helps!