Just to bring this up, as the Jr. Gent 2 has been mentioned, and the CSUSA Apprentice vs Artisan lines, and I have a feeling the Apprentice Jr. Gent may be what you are referring to in the $5-7 kits. There is a lot of confusion around the naming of these pen kits, so hopefully this will help you not fall into some of the pitfalls others have...
The CSUSA Apprentice Jr. Gent is NOT a lower quality version of the Artisan Jr. Gent 2 (!!), they are 2 entirely different sized kits.
The Apprentice Jr. Gent uses the same tube size as the Baron/Navigator/Sedona line (and probably others) but uses different bushings, as the body of the Apprentice Jr. Gent is tapered while on the Barons, both ends are the same size. They ares a good bit smaller than the Artisan Jr. Gent 2 pens. The Apprentice Jr. Gent (often referred to as the Jr. Gent 1 to distinguish it from the 2, that most people don't bother saying...) in chrome is CERTAINLY worth the price ($6) when you want to make less expensive rollerballs. IMO it's biggest distraction is the black enamel threads, but that is a personal preference. I like the size of that line for a shirt pocket carry for it's smaller size.
The Artisan Jr. Gent 2 is certainly a step up in "significance". My wife claims it to be a "Man's Pen" as she thinks it is too large for a woman, but that is open to debate (and she thinks the full size Gent is for when the "Governator" wants a pen, and hates rollerballs in general...) It is a larger pen, and in it's Black Ti and Rhodium versions, they make very good looking pens, and the new Chrome version makes a durable less expensive alternative to the normal gold.
Another thing to keep in mind if you are looking to expand your kits is the other materials needed. The Apprentice Jr Gent uses 25/64" and 15/32" drill bits, the larger of which will also do things like the artist sketch pencil (one of my favorites...) and the smaller half of the Full Size Gent/Statesman, and the smaller one will do both Apprentice and Artisan versions of their cigar pens, and probably others from other places, but I'm not up on all the pen kits... The larger Jr Gent 2 uses 10.5mm and 12.5mm drill bits, which are the same as the Jr. Statesman, Jr. Retro, and Venus if you decide to try more expensive kits. They will also do pens from other Mfgs like the Tritons and probably a lot of others. the 10.5mm drill bit is used for the Zen, Magnetic Vertex and again, probably a lot of others... So sometimes the decision on what pen kit to expand to can be nudged in one direction or another by what other opportunities it brings with it...
Hope this helps and doesn't confuse things more...
; and Chrome/Gun metal.
