Welcome to ECF, imata!
You've asked for a recommendation for a "good" starter kit. The problem is: 'good' is in the eye of the beholder. But based on your stated criteria and budget, I'll share with you my thoughts and, most usefully, point you to a few information resources (not quite as "overwhelming" as the entire e-cigarette-forum) so that you can make your own, informed decision. [You are
not alone in being overwhelmed by all the options.

]
Your question happens to be quite similar to one we just answered. Take a look
here to see how frogbmth and I responded to "buying an e-cig for my mom for Christmas. help?"
You stated that the person in your life is older, a heavy smoker, and not good with technology. Therefore, you want something simple to use, as well as economical and easy to order; and you want to keep the initial purchase under $100.
Most e-cig models (other than the battery "
mods") sold by the suppliers participating in ECF and used by our members fit those criteria. The technology of an e-cig is like a basic cell phone: complex in design and manufacture, but very easy to use. The upfront cost can be
less than $100 and the ongoing cost can be
less than analog cigarettes ... for a
heavy smoker, probably
significantly less (e.g., $20 - $40 per week for
e-liquid and replacement parts; compared to one to two cartons of cigarettes). Any e-cig an ECF member would recommend is purchased online; delivery often within two to
three days (
other than during this holiday season!

).
The very
simplest electronic cigarette is a two-component cartomizer model (battery + combined cartridge/atomizer), like the KR808D-1. But the usual three-component models (battery + atomizer + cartridge) are pretty simple as well. [I'm 63, very non-technical, and
I figured it out.

] The very popular Joye510 (also mentioned in that other post) is an example of that configuration.
I suggest that you read (or, at least, browse) the WWV Illustrated Guide linked in my signature. It provides an overview of electronic cigarettes and the e-liquid that goes in them.
Part 4 may be especially useful, since it points out the pros and cons of each category and model of the smaller devices and includes examples of where you can purchase them. The second half of
Part 5 does the same for e-liquid (especially for where to get samplers) and
Part 6 describes accessories and some newer models and e-liquid suppliers.
Read/watch reviews in the
E-Liquid Reviews,
Model Specific Discussion, and
Video-Reviews forums. And explore the forums of the wonderful
Supporting Suppliers to find out
where to get all this stuff.
And give this "gift that keeps on giving" - in so many ways - to this person in your life!