After thinking things through even more, it's possible to get away with just the 2.5Mm omni-directional antenna called the "Communotron 16" and the 500km Reflectron DP-10 (that gets you off the pad).  Just toss up four cheap satellites in 700km altitude orbits along the equator and at least one of them should always be in range of KSC to relay commands to the other three.

That reduces the power needs to just 0.14 EC/s.  At an altitude of 700km you only need 106 EC of battery power to get through the dark period of the orbit.  You can likely also get by with a tiny amount of solar panels (as few as six, but 8-12 would be better).

The big advantage of a LKO (Low Kerbin Orbit) satellite network is that omni-directional antennas form a mesh network without any manual intervention on your part.  Each satellite automatically starts talking to any other vessel within 2.5Mm and with LoS (line of sight).  Without the use of directional antennas, you are limited in range, but having a mesh network in LKO ensures that any robotic vessels can be controlled at Pe (Periapsis).

Rough cost is about 4055 for the payload (2230kg) with a T200 fuel tank (2279 Delta V).  Total launch cost is 11399 with the (2) BACC SRBs, but you get about 1048 back per booster with the addition of the Mk16 Parachute on top (and the Stage Recovery mod).  I also get back about 2995 of the cost of the second stage (three T400 fuel tanks and a LV-T45 engine).  That puts the net cost to orbit one of these satellites at only 6308 per launch due to use of the Stage Recovery mod.  Keeping the costs low means that you can put up four or five of these fairly early in the game.  You might even be able to use them to fulfill "orbit" contracts if the orbits are smaller then 2.5Mm (2500km).

The total Delta-V from your boosters plus your second stage needs to be at least 4500 m/s (and 4550-4650 m/s has a bit of a safety margin).  You want your boosters plus second stage to barely get the payload into orbit.  The payload itself only needs a T100 fuel tank and the LV-909 liquid fuel engine.  The goal should be to have about 1000 DV left once you achieve a stable orbit (Ap and Pe both above 75km).

If you want more fuel for orbit maneuvers, anything up to the size of a T400 tank is probably okay.  You may need to go from (2) to (3) BACC SRBs in order to lift it.

Launch:

Turn on the SAS (with the "T") key and press [Space] bar to launch!

Initial SRB phase is simply "hold it vertical".  You'll often have to damp out some pitch, yaw and rolling.  Possibly a lot due to how the BACC SRBs work.  That should get you up into the 8-10km altitude if you have a good TWR (Thrust / Weight Ratio) and hopefully not too far off vertical.  If you have trouble, put some more "Small Inline Reaction Wheel" units in.  At least one of those SIRWs should be in the final payload stage.  The rest can be below the decoupler above the second stage fuel tank.

Once the LV-T45 engine of the second stage kicks in, control gets much easier because it has vectored thrust.  At around 10km altitude, I gently start my gravity turn.  My target at 20km is around 10-15 degrees off vertical, slowly increasing to about 30 degrees at 40km.  Once the Apoapsis (Ap) value gets above 80km, I start to turn even more and will try to have an angle of about 60 degrees from vertical as I pass through the 70km altitude.  My target (Ap) altitude is anywhere in the 80-150km range.

As soon as you get out of the atmosphere (70km-75km), you should cut the engines and coast until Apoapsis (Ap).  Now is a good time to deploy the "Communotron 16" so that you have a link back to KSC out past the 500km range of the DP-10.

Note: If this is your first LKO (low Kerbin orbit) satellite, or all of the other satellites in orbit are below the horizon -- make sure you keep thrusting at 100% power until your Periapsis (Pe) is above 75km.  Then immediately stop all thrusting and put the satellite into a good solar power collecting configuration (turn the satellite up or down so that its long side always faces the star as it goes around in orbit).  If the orbit is stable and the satellite is oriented properly with the SAS left on, you have multiple orbits in which to figure out what you need to do next.

I suggesting putting up (4) satellites right after each other at about 1.5 hour intervals (Kerbin has a six hour day).  Get the four of them into stable orbits after launch, then start to worry about boosting them into their final 700km altitude orbits with proper spacing.

The second in-orbit burn for each satellite should be one that raises the (Ap) to 700km.  Leave the (Pe) value at or greater then 100km altitude.  You will want to leave the satellites in this elliptical orbit until it is time for orbital insertion at the (Ap) node.  Think of orbital insertion like trying to merge with freeway traffic with the advantage that if you do not like the spacing, you can just let the satellite go through another orbit and try again at the next (Ap) crossing.

If your satellites are all bunched up and in circular orbits, you can spread them out by:

- Doing a prograde burn on the tail-end satellite.  This will push it into a slightly longer and more elliptical orbit which will slow it down compared to the rest.  If you are looking for only a minor amount of spacing, pushing the (Ap) up by 10% will probably be enough to do the job in a single orbit.

- Doing a retrograde burn on the first satellite in the line.  This pushes it down into a slightly lower orbit which gets it around faster then the others.  Do not push the (Pe) down too far (more then 5-10% of orbit altitude).

The same tricks hold true for a satellite in KEO (Kerbin Stationary Orbit) where you want the satellite to stay over a specific point on Kerbin (usually KSC).  If your satellite is running ahead of KSC, then put it into a slightly higher orbit for a while.