There are numerous resources available, including the ARRL Antenna Book, that will help you make the right decision. Those that have spent hours digesting the published material know that likely your best option for a multiband antenna will be a ladder line (or open wire line) dipole 1/2 wavelength high or higher on the lowest band you intend to work. Spend the trivial amount of money on the Antenna Book. The information is invaluable. There's a user here, KJ3N, who uses a ladder line fed dipole and works some outrageous entities that I have to use a beam to catch. Yes, location and height is a factor, but such antennas work well.
I've used SEC power supplies. They're small and lightweight and work well. I'm going on five years using one with meters. I think I spent $125.00 for it.
If you feel 100 watts is going to be your max for a while, MFJ, which may be of dubious quality, has plenty of tuner options for you to choose from which are relatively cheap. I spent $150.00 for a used MFJ 962C. Later, I spent $550.00 on a Palstar AT2K. The Palstar's quality is obvious over the MFJ, but they both do the same thing.
In terms of coax, I like to use DXEngineering RG213 or 400 max. It's not cheap, but it's quality.
Finally, ask yourself what you hope to achieve. If DX is your ambition and if you're location will permit it, a small 2 element beam will easily outperform any dipole or vertical you can erect. There are five band beams available for under $500.00.
You also may want to save for a while longer and look at something along the lines of a Yaesu FTDX 1200, Icom 7410, or even a Kenwood 480SAT over the Icom 718. I believe the 718 is getting a little long in the tooh.