Clearly the most important thing to start with is a cocktail shaker! There are of course cocktails that you build in your glass but you will be glad you’ve invested in at least two shakers.
A small shaker means that when you are making a short but deadly alcohol only cocktail such as a classic martini, or perhaps the cocktail blend that goes straight into a champagne flute before adding fizz, you won’t be leaving too much behind or on the ice.
Something a little larger will be useful for when you’re cocktailing in company, or you just know you’re in the mood for "three" martinis all on your lonesome while watch Netflix.
And really, if I’m honest, you can get away without anything else, but if you’re looking for an excuse to shop, you could add these few things…
No matter how good the strainer is on your shaker, you will want to buy yourself a separate one too. Buy one that feels good in your hand rather than looks the part: my favourite is the first one I found and is probably the cheapest. Salad tongs or a slotted spoon are good options if you don't have a strainer. But if there are muddled ingredients, you may want to use a finer kitchen strainer.
I like to have a number of different sized measures just in case I’m being super organised and measuring everything out before mixing. I have a lovely crystal 90ml measure, a whole pile of glass 30ml measures, as well as a couple of larger ones. Always remember to use the same measurement within each cocktail: mls, tablespoons or teaspoons etc.
Again, I’ve a couple of these but the one I use most often is a simple cheap white plastic version. For cocktails for the two of us, it really is enough and is so easy to clean.
I also have a much more professional electric thing which I do use ahead of cocktail parties, but it sits looking lovely on the work surface for most of the year and probably not worth the investment if you’re only cocktailing every now and again.
Santé! Cheers! Enjoy!