Hello and welcome.

If you have existing siamese cable run to the locations, then you can do either a traditional analog system with 960h resolution or you can go with the newer technology and do HDCVI.  The advantages of HDCVI are that it will offer you HD images over the existing coaxial runs.  You can choose between 720p or 1080p resolutions.  The entry level would be going with a basic economy level HDCVI DVR and some 1MP HDCVI cameras.  Now are you looking to only do the 3 camera locations that are wired or are you looking to expand in the future?

If you are looking to expand in the future, I would suggest going with an 8 channel recorder to save you money in the long run.  You will need a few supplies to complete your install.  

The short list is: BNC Connectors {(Twist, Crimp, or Compression) 2 per camera}, power leads (definitely a PT-3 per camera and depending on how you are powering maybe even a PT-4 per camera), power supply ( either a distribution box or plug in play transformer), and the DVR with a HDD.  You will also need some basic hand tools.  You will need a wire stripper for the coaxial cable as well as for the 18/2 cable.  You will want either some B-gel connectors, wire nuts, solider, and/or electrical tape for connecting the 18/2 to the power leads.  You will need at the minimum a couple of screw drivers, I suggest a drill.  And unless you are extremely tall or the locations are extremely low you will need a ladder.  If you want feel free to call our sales team and we can walk you through getting everything you may need for the install and best pricing possible.  We are here from 9am - 8pm EST.  We can be reached at 1-866-573-8878 option 2.

I hope this helps and once again welcome to the forum.