The biggest hurdle to streaming efficiently is having the right hardware, so that's where we'll start. Streaming software and services have come a long way in ease of use, often at no cost, but there's no getting around the fact that you'll likely need to purchase a few physical items to bring your streams to life. The single biggest obstacle and item is a powerful enough PC. There are many things that go into a computer that make it suitable for streaming, so this requires the most detailed explanation.
This system will likely do double duty as your gaming and streaming machine (more on that later), so it needs to be fast. If you're planning on streaming PC games, it should be obvious that your computer will need to be up to the task of playing modern games as a minimal baseline. This is the most expensive item you will need for transmission and there are many factors that go into a decision.
Generally speaking, your ideal streaming laptop can run games at high, if not maximum settings, in your chosen screen resolution. You want your broadcasts to look their best, and if you want to showcase the latest AAA releases, eye-catching graphics go a long way to entertaining viewers. However, you don't need to go broke if you can't afford it. Moderate gaming rigs will run games moderately well, and if that's your budget, that's fine.
Most streamers play in Full HD (1920 x 1080, or 1080p resolution), and I highly recommend that you follow suit. It's a lot less demanding on your computer to play 1080p, which is essential, as it may also have to bear the burden of processing and pushing your game streams. Plus, you'll get much higher frame rates in game than you would at 1440p or 4K, which means smoother looks.
Please note that the resolution of on-screen games may be different than the resolution that streaming is set to. It is very demanding on both the PC and your Internet connection to stream in Full HD or higher, which is why you will find that many streamers opt for 720p or 900p; even some of the biggest names do. Most popular streamers can afford to invest in a PC and internet connection that can generate super-sharp streaming, but don't feel like you're the only one who may have to make a compromise.
If you're the type to stream competitive multiplayer games (titles like Apex Legends, Counter-Strike: Global Offensive, Fortnite, or League of Legends), visual fidelity matters a bit less, but performance and high frame rates are vital. You should be able to play smoothly as it will give you an edge, which is especially important if you advertise as a skill-based streamer. Playing 1080p and taking advantage of those higher frame rates is even more important for these types of gamers.
If this is you, pairing your setup with a high refresh rate gaming monitor is a smart move. In fact, many competitive streamers (even those with powerful PCs) play with low visual settings to improve frame rate, as it means a competitive advantage for them. Still, even if you're gaming on low settings, you need a high-end computer to take advantage of a high-refresh rate display. The video card in the PC is key.