The 50 is a good portrait lens on DX, where it gives a diagonal field of view of about 31°40. On FX the FOV is 47°. This means that you will come closer for a classic head and shoulder portrait and this closer distance will change the perspective so that the nose and chin will be accentuated. This looks unnatural as we seldom step that close to each other.
The 85 has a FOV of 28°30 on FX, giving a pleasing rendering of facial features in a formal portrait.
The 50 on FX is more suited to knee up or full body portraits. Nicole posted one in the Your best... minichallenge last week. Your Best Photo, Week Ending 22 July 2018 - Mini-Challenges, Member Contests, and Games - NikonForums.com
A 35 is very suitable for environmental portraits, where you want to include more background.
Any prime between 24 and 200 can be a portrait lens. David Bailey loved the 24 for his style of intimate, up close portraits while high fashion shooters often go long in the 135-200 range.
To decide if you like a 50 or an 85 better for your style, you can use the 18-55 you have on your D5000. If you shoot some portraits with the zoom fully racked out and compose so you don't use the last mm or so in the finder, this will be close to the perspective you will get with an 85 on FX. If you set the zoom to 33 mm, the FOV and perspective you get will be close to a 50 on FX. As the kit zoom is a slow lens, you will have a much too large DOF, but the perspective and FOV will be similar to the primes.
I used my 50mm quite a bit for portraits back when I had a crop-sensor camera, but even back then I preferred the 85mm. With a full frame (like the D750) I would strongly recommend at least the 85mm over the 50mm for portraits. Peter is 100 percent right--if you try to do closeup work with the 50mm on a full frame camera, you're going to get some less-than-flattering results. In the photo that Peter just linked to as an example, I used my 50mm mainly because of the small space I was working in. I would have chosen my 85mm, but I didn't have enough room to get as much of the environment as I wanted--had no choice but to go with a wider lens, and the result was fine because I wasn't up close. Incidentally, I have the 85mm f/1.8 rather than the 1.4. It was much less expensive, and the lens is fantastic.
Here's a thread from dpreview.com with some good illustrations that show the differences focal length can make:
Facial distortion of various focal lengths for headshots: Nikon SLR Lens Talk Forum: Digital Photography Review
Anyway, your initial question was about the kit lens. You might want to buy it just because it is so versatile and it will fill a big gap--even if it's only temporarily as you eventually upgrade and buy more lenses. Of course, it depends on your shooting style and subject, but you might feel a bit limited if you only have a 50mm to work with, especially for travel and landscape photography.
Your favorite things to shoot are also my favorites. I think if I were in your shoes working with the preferences you've already expressed, this is what I'd buy:
1) Kit lens 24-120 (versatile for travel and landscape)
2) 85mm (excellent for portraits)
3) 35mm (if you're thinking about this for portraits, just know you'll want to use it for environmental portraits, not closeup shots)
Anyway, good luck with everything and keep us posted on what you finally decide to do--and we'd love to see you share some of your work here in the forums.
Let me start by saying how thankful I am that you both took the time to help me out! I really appreciate the perspectives that you're offering!
Peter and Nicole,
The idea of including more of the background in my portrait photos was one of the primary reasons I was considering the 35mm lens at all- that, and I thought that if I could only get one lens, this one might be able to double as a decent lens for landscape photography. However, with the idea of going ahead and snagging the kit lens, that would give me the opportunity to snag a more suitable portrait lens and still be able to get my landscape shots! The 85mm is looking more and more attractive!
I'm most interested in maternity, baby, and family portraits. I'd also love to do engagement shoots- I enjoy the idea of capturing the landscape in a little more focus sometimes, so that's why I started out most interested in the 35 and 50mm lenses. Though now I'm leaning toward the 85mm and kit lens combo!
Below are some examples of the types of shots I'm after. (These are not my photos!)
Below are a few recent shots from my D5000 and its 18-55mm kit lens. I can only get soft bokeh when I get very close to a smaller subject. Sometimes I wonder if investing in a new camera is worth it when I'm more of a hobbyist than anything, but have just felt very limited with the D5000+18-55mm lens lately.
https://scontent.fca...cbb&oe=5C0ACF2B (I'm proud of this one! Taken at 45mm/5.3 all up in his personal space.)
Thanks again! I really appreciate the help!