Simple parts for 3D printing can be done with TinkerCAD. A free and basic CAD program that can do what you want. It runs in your browser window so it's platform agnostic also. Though I will tell you phones and tablets are very poor tools to do CAD work in. Larger screens and a mouse are virtually a necessity if you intend to not get frustrated.

After that, Fusion 360, (Windows only and a bastard install of local and cloud requirements), is popular with 3D printer enthusiasts. It's a stripped down version of AutoDesk's professional tool. There is also OnShape, another full CAD program that has a free license that runs in a browser window like Tinker CAD. The UI is a bit harder for newbies to navigate than Fusion. But there are limitations to hobby users.

FreeCAD is open source and a local install with support for Windows, Mac, and Linux. Newbies tend to find the CAD concepts difficult, (mostly because they are based on more proper workflows and design knowledge. FreeCAD will often punish sloppy workflows of beginners). And newbies tend to find the UI confusing. But they are working on it. The latest 1.0 release features a lot of improvements that user have complained about for years. But the learning curve is still steep and it takes some effort for those without real CAD experience and an unwillingness to practice the craft.

That said I forgot 3kkk which has a nice 100 quick tutorial. They are pre V1.0 but should still be useful!

https://www.youtube.com/channel/UCk0gfSbL5xF9kv7_lc2Ob_A

I can't say one or the other definitively, I think it depends on who you like listening to the best. What I would do though is try to do one short tutorial a day for a while instead of longform videos. That tends to yield better learning results.

I feel like it's finally at the point where the issues are minor enough that I have the patience to deal with them. I've been using the release candidates for the last couple of weeks and mostly it comes down to remembering to save regularly and occasionally having to shut it down and restart. Honestly, some of the commercial solutions aren't drastically better in that respect!

I think anyone coming from a place where they have a ton of experience in SolidWorks or Fusion might want to hold out a little longer, though it's definitely worth a try. If you're coming from a place where you have to learn a new program anyway, you might as well learn the free option that will only continue to improve.

I half pay attention to freecad every few months because I do think it is genuinely a good project to exist. And while I think it is a borderline anti-pattern, having "hey, let me control this like it is that program" is a good shortcut for low budget projects.

And... I still think Angus's (Maker's Muse) FreeCAD video really hits the nail on the head. https://www.youtube.com/watch?v=p8Pk1ayx6LQ

A lot of it, on the surface, is "open source weirdness". And... some of that gets fixed. But it is his comparison to Onshape and Onzel (?) that really are why I actively discourage newbies from even trying FreeCAD.

Because if you know what you are doing? You can figure it out. Stuff like "oh, the default extrude is probably going in the wrong direction" or "one of the steps of my parametric build errored out. Let me step through and find it". But that depends on knowing what you are doing in the first place. So newbies aren't learning "CAD". They are learning FreeCAD.

Whereas giving someone TinkerCAD or Onshape or Fusion 360? They are learning fundamental concepts. The UI/UX is such that most operations are "intuitive" once you understand a few basic concepts (mostly extrusion) and the error messages are generally good to let you realize where things went wrong.

And... while I very much do agree that a product that can't be licensed our clouded away (even if it could still just as easily die tomorrow) is important AND disagree that piracy is a solution (in large part because of the heavy online component of stuff like fusion 360 to specifically stop piracy...)?

if Onshape dies tomorrow? I'll be pissed. And then I'll look for an alternative and more or less hit the ground running. And that alternative might actually BE FreeCAD. Because I know enough about modeling and design that I know what pitfalls to check for.

Whereas someone who learned FreeCAD and nothing else? They are now figuring out that padding is extrusion and unlearning countless other quirks.

And the other aspect? There is no reason for a hobbyist to actually put the effort in to learn something like FreeCAD. Tinkercad gets mocked relentlessly but... it is insanely user friendly and is more than good enough for what most people are going to be modeling on their own. And it is specifically designed as a path to fusion 360 once people realize they need to know what an assembly is. And Onshape exists too.

This isn't a case where your options are Photoshop or MS Paint and something like GIMP is MORE than worth learning (... even if paint.net might be the better hobbyist choice as of the last time I looked). The free entry level market is, arguably, saturated for CAD programs. And early on as a hobbyist? You just want to Make. You don't want to get hung up because of software quirks.

And if someone wants to turn this into a career or a side hustle? That is even more reason to learn a more industry standard workflow.