It's not generally a good idea to mix only a portion of a powdered chemical and save the rest for later, for a couple of reasons. First, the chemicals making up the powder may not be evenly distributed in the package, and therefore each partial batch can have a different chemical composition. Also, the envelopes the powders come in will no longer be airtight, and humidity and oxygen will cause the chemicals to deteriorate. It's better to mix it all up at once, then store it in smaller bottles. With Developer, it's especially important to keep the bottles full and tightly capped, because the oxygen in the air will cause the developer to deteriorate. If you leave developer in a tray overnight, it may not be any good in the morning. I've heard of people laying plastic cling-film over the surface of the liquid to keep the air out, but personally, I just either pour it back in the storage bottle, or throw it out, depending on how many times I've used it and when I expect to use it again.
Kodak products will list on the package an expiration date for the powder in the envelope, and also an amount of time you can store the stock solution and working solution under ideal conditions. Heat, light, and especially oxygen will shorten the life of developers. Also, as you use the chemicals, they will lose effectiveness (especially developers) as well.
If you're worried that you might not get to use all the chemistry before it goes bad, you might consider either buying smaller portions which you can use up before spoilage becomes an issue, or perhaps try liquid concentrates, which seem to last longer. An old trick for eliminating air from a partially-used bottle of chemistry is to fill it with clean glass marbles to bring the level of the liquid up to the mouth of the bottle.
The enlarger kit doesn't appear to come with a timer; you'll want one (I personally would say "need"). The timer will allow precision timing for your print exposures (meaning consistency). Also, keep in mind that when you're handling undeveloped film, you want absolute darkness; glow in the dark dials such as the one on the timer you have listed (and on wrist watches) can fog film, so you'll want to cover them. Also, do not use fluorescent lighting in the darkroom, as they have residual glow when you turn them off. Tungsten lighting only.
The measuring graduate seems awfully expensive. I use a plastic measuring cup from Wal Mart, and I've never had a problem with it. I clearly marked it "photo only" so it never gets confused with kitchen measuring cups. You might be better off getting some one-gallon (or smaller, if you're dividing up your chemicals into smaller portions) plastic jugs for chemical storage. They work well, and cost much less than the tanks you have in the list.
Finally, I'd seriously suggest putting a radio in your darkroom. I find that it makes it much more comfortable. Oh, and as ferny says, you'll need a thermometer. And don't forget a shelf for your reference books.
Just curious, how big is your darkroom going to be? I've got mine set up in a 4-foot by 5-foot closet... kind of cramped, but it works pretty well. Wish I had running water in there, though...
I haven't run into any problems yet.
