>>1647179lol me in 40 years
>how to clean grips (and bikes in general)get a bucket of hot soapy water (dish soap is fine) and a rag. For cleaning things with tacky residue or oil type crud that doesn't come off easily, use either an aerosol degreaser you spray on and wash off with water (the stuff for cleaning engine bays is quite good), or, more often, a solvent like kerosene.
You could just treat yourself to some nice new grips. I like the silicon type like Redmonkey Karv and i like oury. And you install them with isopropyl alcohol as a lube to slide em on, which will evaporate out.
As for tires, well, that's the best place to spend money. It's 700c right?
get some tanwall panaracer paselas, as wide as will fit.
As for the valve issue, you can use presta valves in schrader holes (which are wider) but the valve stem will pull through and is prone to damage there. So you want a grommet there. You can buy specific ones. Grommet.
That looks like a relatively cheap saddle. I would replace it. Another place you could splash some cash would be on a b17 brooks. Some people hate them, but they are the ultimate in comfort and style. And you can resell it easily if you don't like it. If you don't want that, I would look at mtb saddles, which will have some padding, but not excessive like WTB volt.
I'd also splash money on nicer pedals. I like the more expensive (smoother bearings) nylon/plastic ones for bmx.
To spend money on servicing, check all the bearings, if any are rough of with play, you cuold pay a shop to do them, or do it youself. Other than that, buy a chain wear tool (~$5) and some chain lube and keep on top of that. And ride it.