Run a system cleanup and Defrag. Defrag may take a while spending. If you have an Antivirus program, use it. If you don't, download one such as AVG free edition. There is a program called CCleaner that is very helpful for cleaning up junk files and repairing registry erros. A program such as spybot search and destroy is a good way to rid your pc of any spyware. All these examples are free to download basic versions of and are very helpful. Last any maybe most importantly run MsConfig from your start menu using the search bar or run program bar. Just type it in "MsConfig" when the program starts up find the "startup" tab and disable everything in that list. This will stop any non essential programs from running in the background. I use all of these techniques for easy pc management.
You can try change Ram.. Is a very easy process. If you don't want to pay any money Razer has a program available to download for free that accelerates games and improves your gamig experience.. You should give it a try It also depends a lot of your Video Card and the quality you want run them (games).. For example is not the same running a Battlefield 4 than running a flash game.. Good luck any question feel free to follow me
What type of setup are you running? CPU = ? Ram = ? GPU = ? HDD = ? If you are running an old chipset there may not be too many things that can be done to upgrade your system.
Try cleaning the inside of the PC, any dust building up makes the PC hot which slows it down. There are instructions on the internet or you can bring to a PC repair place.