When buying a PC or a Mac today, DO NOT make any compromises on the type of hard drive it has!
Make sure it has an SSD (Solid State Drive)!
For most regular users, 256GB is sufficient if you're on a tight budget.
If you have HDD, you can buy an SSD and add it, most computers have the provision of adding in another hard drive. Do that and put the OS on the SSD and have an improved experience!