Staining/painting won't really move the needle much on curb appeal. What WOULD help is some sort of covered porch at the front door, but that may cost more than you want to spend and may not be worth it. Landscaping would be the most bang for your buck. But the only reason to worry about curb appeal is if you are planning to sell. If you're not, I would put the money into landscaping.

Is the rest of the house (back and sides) brick or siding? Is the siding aluminum or vinyl?

The cool toned gray roof isn't playing nicely with the warm toned siding and brick.

I agree that that landscaping is needed. Evergreen shrubs to soften the look.

It's not recommended to paint vinyl siding a dark colour, because of the possibility that it will warp. Aluminum siding can be painted any colour.

The brick is a feature you plan around not paint over. The current vinyl color is blah but if it stays the trim has to stay white. Find a great punchy color for the front door (orange, purple, aqua). If you can stretch get a great looking garage door. Other than that all dollars should go into landscaping.

I'd paint the door a warm color. The stark white doesn't go with the brick. Maybe a peach that's darker than your siding and picks up tone in your brick. I'd paint the garage door, too. I would never paint/stain brick (a nice exterior finish) to match vinyl (a much less nice finish).