Hi, and welcome to the forums.
Questions:
1. What do you want to be able to do with your machine? That will determine the specs you'll need in terms of CPU, RAM, hard drive and video capability, as well as specific ports you'll want, such as HDMI for video or USB3 or Firewire for higher transfer speeds to external devices.
2. Where can buy your machine? Can you buy good machines locally? If you intend to buy from another country, it will have to be one that can ship to your location. That will determine which makes and models you can actually buy and how much they will cost, including both the base price and shipping.
Another issue you should consider is which manufacturers are able to provide technical support in Algeria (or wherever you intend to use it)?
Your answers will help us to give you more useful info.