Use rocks glasses when you want to muddle ingredients in the serving glass, and as a general rule for drinks served over ice balls or cubes. Aim for 6 to 8 fl. oz. If you think you need a double, it means you're drinking two cocktails at a time. Ice melts too quickly for that and dilutes the drink beyond what recipes intend, so buy a single and make the second drink when number one is gone. Cocktails are meant to be enjoyed quickly, after all. Example drinks: Old-Fashioned, Bramble, Negroni.
The Collins glass is so closely related to the Highball glass, which is slightly wider and squatter, that you only need one or the other. Because drinks fit for a Collins or Highball glass are served with lots of crushed ice, these should hold 10 to 12 fl. oz.
Sometimes used as a measurement for syrupy ingredients–e.g. “one bar spoon of pomegranate syrup”–its main purpose is to stir drinks; 30 cm is the standard length for your standard-sized mixing glass. Too short and your sleeve cuffs will be taking alcohol baths, too long and you'll look like Pee-wee Herman mixing a drink.
Unless you're using a mallet and ice pick to chip your own cubes, spring for the ice trays. The 1.25-inch option is standard for ice used in mixing a cocktail.
At least a half-liter mixing glass is suitable. A decent glass will be thick enough that a metal bar spoon banging around inside won't shatter it. Just make sure it has a pour spout so that when you serve the drink, you empty it all into a glass and not onto the rug.
Buy the Boston type, in which you hold together two parts that look like metal pint glasses. You can make all shaken drinks in these. Skip the cobbler-type with the built-in strainer and cap. It can't do anything better than the Boston shaker, except look cooler.
The Hawthorne is your go-to tool for separating cocktails from extraneous ice and ingredient remnants as you pour from a mixing glass. It fits against the rim of the mixing glass like a lid.
FINE MESH STRAINER
Occasionally you need to filter out certain ingredient debris that slips past an ordinary strainer, like fruit shards and egg. The fine mesh strainer is held over the serving glass, and the ingredients are poured through. You won't use it often, but when you need to, it'll be the only thing that works.,
Japanese jiggers weren't originally Japanese, but when Western bartenders rediscovered their Japanese counterparts using them in the 2000s, they fell back in love with the two-sided measuring tools. They have different capacities on each end, so you can buy half as many as you'd otherwise need. First get a ½ fl. oz. / ¾ fl. oz. jigger.
The world's best bars use expensive base spirits. They use Rume, Whiskey and Grey Goose Vodka. Do not forget to grab one Grey Goose limited edition 2018.