As a professional Mindforce user I would like to strongly suggest you go with Rifle to start your career and then doubleback to Mindforce after you've been in the game for a month or so.
Mindforce isn't as well developed as Rifle or Handguns are. There aren't as many top end items to be used (both attack and heal.)
As far as what and where to buy: where would be via auction.
What is up to you. Generally speaking Mindforce attacks break down into 3 groups:
Pyro (Fire and Corrosion)
Electro (Kinetic and Electric)
Cryo (Lacerating and Cryogenic)
Each has its +/-. For example, Corrosive Chips have a very short range but very fast rate of attack. Kinetic have medium range and medium attack. Etc.
This thread may help:
https://www.planetcalypsoforum.com/forums/showthread.php?251506-The-Different-Types-of-Mindforce-2-0
My suggestion, if you're going to ignore the one on starting with Rifle, would be to start with a Corrosive Attack Nanochip I. A healing chip would be Regeneration Chip I. Plus, you'll need an implant which you can buy at a blue Trade Terminal Neopsion 10.
But to belabor the point a far better plan would be after you download the game to do the Gateway Missions. Once you're out of the Gateway start on exploring your home planet (I'm on Calypso). Collect all the teleporters. Get a mentor. Then start sweating, chatting, and looking in auction to get a sense of the game economy.
After a month if you want to give it a go then buy the Gold Starter Pack from the webshop. Use the armor and rifle/amp/scope and healing pack combination there and do the Puny Mission Chain. If you finish that then make the switch to Mindforce if you still want.
Good luck