Start with the expensive stuff. However, make sure you have to replace, rather than repair, on some of it to save cash. That "planter" in the corner is some type of vent, which was disguised as a planter. The vent may be obsolete, but be careful before you rip it out. The second door into the house by the garage makes sense, so that people don't have to track through your nice living space with dirty shoes, or stack up all their stuff right by the front door, so keep it. Enlarging the windows above the garage to better match the rest of the windows makes sense, as you plan to replace the siding anyway.Can't quite tell your brick and roof color from the photos, so difficult to give color ideas. As to siding, a good quality vinyl is good, but many people are going with hardie board.

The roof is brown/black and the brick is orange. 3rd picture is a true color of the brick.

If you can take a better image of the front of the house we may be able to show you some ideas.

You have a big job ahead of you but to start:

As it is I see a bike in the lower entrance. Would be great to have a portico gate there for the kids.

I'm also thinking the color of the door above would be great for your trim work.

On the upper portion of the house stucco would be fantastic.

Adding a overhang to the garage would break up the plain expanse and help to even the look of the home.

I agree that changing the facing of the garage and above would make a big difference - also it's nice to create a more formal entrance to your front door - instead of the rail that's there...consider doing a brick wall/entrance with lighting and carry the brick walk to the front door. Also if there's anything you can do to the 2nd story inside to change the roof line - either with doormers or something like the overhang for the garage...I've added a photo of an entrance we did from our driveway and then we just had the driveway sealed black to make it look nicer - getting new outdoor light beside a new garage door can really help too...

I see some neat contemporary lines in the windows, doors and mcm block. Nothing traditional like stucco or wood bracket supported overhangs seems right to me. The crack in the block can be parged out and regrouted by a skilled mason - the vent for your basement may have been for a past HVAC unit, given the proximity of the compressor. Have a heating and cooling specialist look to see what venting is currently in place, compared to what needs to be in place before you demo.

I am not a fan of the diamond elements on the garage windows, the garage wants to be as contemporary as possible, and to do that with terracotta brick is probably a warm gray on the outside siding and fascia to contrast with the white windows and entry . paint the lower door the same warm gray to fade in - I would not keep that - family would use the garage door first . . turn it into a window using the "corner planter" brick as the bottom half of the new wall . . .

Do consider tearing out the existing concrete stair and retaining wall opposite the brick planter . . excavating a wider stair that sweeps like a pie forward . . here's a suggested siding tone to work with the brick and white http://www.benjaminmoore.com/en-us/paint-color/dolphin

if you want to do something, you could do a contemporary white arbor - hung from above over the garage . .