shampoo and vacuuming your interior would be the best way to go. doesnt seem like youre talking about stains but rather dirt and dust thats accumulated over time. might be a bit pricey if you dont have your own shampoo vacuum. besides that, since your cars interior is cloth, it'll naturally create more dust. make sure you just dust your car pretty frequently (once every other week at least) on the hard surfaces like your dash and door panels. i like to use those swiffer dusters b/c they pick up a lot w/o scratching surfaces or using sprays or other cleaners.

since your car is fairly new, just use a regular hose (no high-pressure) and as mentioned before, a rag to wipe things down w/. if you dont clean your engine area for several months/years, you might need a degreaser to break down the grime. make sure its diluted properly (if necessary), spray it on the underside of your hood and other dirty areas, let it soak, spray w/ water, then wipe down.

avoid getting water on your alternator, battery, and if you have a CAI, that too. you can just cover it w/ your cloth while you spray away, just so long as it doesnt receive direct jets of water. dont worry if they get wet. you just dont want to soak them too hard.