I am from Bangladesh and I can't chose according to budget.
First, I am want to know what makes a laptop faster or help for better performance then chose with Budget.
Faster CPU, more/faster RAM, faster hard drive, faster video card, more modern interfaces, there are a ton of things that make a laptop faster. It's pretty simple, the faster the components, the faster the computer. You can't just pick one thing, and even then that one thing may not matter such as faster clock speed since not all CPUs perform equally. The Pentium 4 CPUs run at a fast clock speed but are very slow compared to slower clocked newer CPUs.
If you want a general idea, a laptop in the $600+ range will be a good starting point for a laptop that can handle many tasks OK, 800+ for something that will be good all-around.
You are better off listing your budget and then asking what system would be best for you. You had a question about a W530, that would be good for you for a cheaper used system. What is available for you also depends on the area, there are hundreds of system variables and models and even more if you look at used systems since those vary greatly in price and what is available in your area.