420, eh? Niagara Falls?
Rule Number One is: If you like it, it's good. (No guarantee you won't ever get laughed at, though.) That applies to whisky, glassware, and significant others.
That said, most of us feel that a tumbler is not the best glass for appreciating whisky. It's designed for ice, which is a no-no. (Unless you like it...ha ha ha! Sorry.) A glass with a tulip-shaped bowl retains vapors for nosing, which is an important part of appreciating. Go down to the thrift store and find yourself a couple of 99-cent brandy snifters. If you feel a little self-conscious using them in front of your friends, well, then hide them and use the tumblers until they go home. Or laugh at them for being such unsophisticated goobers.
Water is a much-discussed issue. Experiment and see what you like. There's no wrong. I used to use a little in my early days, when I found the drink a bit overwhelming. I almost never do now. Try only a few drops at first, and see if you can detect a difference in the aromas. Don't worry about it if you don't. You can forget about water for the time being if you want, and revisit it when your palate gets a bit more educated.
I've seen some very fine whiskies suggest a ratio of 2:1, water to whisky...yuck! To me, that's whisky in my water, rather than water in my whisky. But it goes to show that there is considerable variety of opinion on the matter. Again, find what you like, whether it's 50:50, a splash, a drop, or none.
Glenlivet is a very nice smooth single malt that will give you an inkling of what a single malt is, compared to a blend. There is wide variety in malts, from light to full-bodied, sweet to dry, flowery, woody, spicy, smoky. The endless variety is what interests most of us. I suggest for starters that you find a bar that has the six Classic Malts (a marketing scheme of Diageo, which owns the six--Glenkinchie, Dalwhinnie, Cragganmore, Oban, Talisker, and Lagavulin--and many more) and try them all. That will give you a small sense of what kind of variety there is, although of course it's just a beginning.
How long to keep a bottle open is another topic much discussed. Some of the lads here have twenty, thirty, forty bottles open at a time, some of which may be open for years. It's possible for oxidation or evaporation to have a deleterious effect over such a long period. I try to keep it to five or six open at a time, for a month or two or three each.
We all like a buzz, to be sure, and we all overdo it sometimes; but yes, appreciation of the flavors is a big deal. If you're aiming for bulk consumption, you might want to keep plenty of inexpensive stuff around. Appreciate a nice malt or two early in the evening, and then bombs away! It's your whisky; enjoy it how you want. Salut.