Ram is pretty much the easiest to upgrade on a laptop. Just make sure you have the right kind of ram. The motherboard usually dictates what bus speeds you can handle. That can be hard to find out on a laptop. There's websites that'll help you , where you can fill in your make and model of laptop , then it'll show you what ram you need. After that you can look for that cheap. Ram doesn't cost you much anymore.
A hd upgrade in a laptop would be easy to do as well. This'll speed loading times. Usually, they put 5400 rpm HDs in a laptop to save battery power. You can still get decent speeds with better rpms with green disks, although I'm not a big fan of them, they work well. I always upgrade to 7200 rpm no green disk for data storage and an SSD for running my OS and programs from. SSD is always a nice choice, if you have the money. ( check
StorageReview.com - Storage Reviews and then pick one from their leaderboard) .
Another thing you could upgrade in a laptop is the CPU. That can be more difficult if the build of the laptop prevents you from easy access.
Those 3 can be upgraded pretty cheap. You can probably score a ram update for about 20 to 40 bucks, a HD upgrade for about 40 bucks ( if you go ssd, this can become more pricy, but today you already have a leading SSD for about 100 to 150 bucks, 256 GB) . A cpu, depending on what you are looking for , can also be upgraded for about 50 bucks , to a lot more
Depending on what laptop you have, it's age, it's speed and how far you can upgrade with the motherboard limiting what ram and/or cpu you can put in it, you'll have to figure out what you want to spend on it.
Ram is the easiest to upgrade which will make working your vsts possible.