3- 5 gear special gearset? So, a while back when I was rebuilding my vintage Shogun 6-speed, I realized that I only use 2- 3 gears on my commutes to and from school, crew, and other daily rides. The next day, I went to my local used bike parts dealer and bought a 10 speed cassette, the type that has the 3 screw- in pins on the back and plastic spacers, and tried different variations of 3 non- lockring gears; one large gear, one medium gear, and a medium- small gear, which with the required 2 lockring cogs makes 5 total cogs. 

Anyway, what I was wondering about is if it is physically possible to have a gearset like this; would the gaps between gears be too big? Is there any way possible to make a 4- 5 speed gearset, and not have the chain fall in between gears or not be able to grab the next one at all?

Also, I'll upload pics soon.
Yes its totally possible.  The single-cog version is one way to make a single-speed on a multispeed wheel.



The downsides are that you don't gain any lateral strength in the rear wheel because it is still offset, and that the single or fewer cogs are pressing into the freehub with far smaller area, so you're much more likely to damage your aluminium freehub.   See How to prevent freehub body damage?

In your case you want a couple of gears but not all of them, so you would fit the 3-5 cogs you want, and then pack the rest with spacer as per the photo.   Don't put spacers between the cogs.   Aim to have the cogs so the middle one is in the middle of the freehub, which will give the straightest chainline.

Then adjust the high and low limit screws on your Rear Derailleur mechanism.  Its quite possible they won't go in far enough, and you may need to find some longer screws with the same thread to do the job.