How do you know what's causing the lag?

[ClickerBoy]

Okay so I have a laptop that I play most of my games on when I'm not on a console, but this laptop is just your normal work laptop and it can run simple games like league of legends just fine, but when I play games like csgo and skyrim and things, I get lag and It's not exactly unbearable, but when you're getting 15-20 fps on a game like csgo, you start to notice. I'm not planning on playing any high end recent games like fallout 4 or anything, just games like csgo without lag. Anyway my question is about what causes the lag that I'm getting? I was considering buying a graphics card or some more ram, but I don't know what I should be getting because I don't know what's causing the lag. I'd like to say that I never have bad ping as I use an internet cable and I csgo used to work just perfect until the r8 revolver update, so I don't know if something changed in the update or whatever. But yeah, is there a way for me to find out what's causing the lag? Thanks for the help in advance

 

[SoNic67]

Run in background GPU-Z (to monitor the video card usage and temperature) and Windows' Task Manager Performance (to monitor CPU and memory usage).
Play the game until it lags for 1 minute and then Alt-TAB to the monitoring programs.
Take a screen grab (Press PrintScreen key) and paste it in Paint if you want to post it here.

PS: You cannot replace your laptop video card. That's why desktops are better for gaming. Or anything else serious.

 

[alth0triplemadang]

wanting to game on a laptop?
your old laptop doesn't do the job well for gaming?

simply buy a new laptop with dedicated video card