If your home bar feels limited, do not always buy another spirit. Add mixers that create range. Soda lengthens drinks, tonic adds bitterness, ginger beer brings spice, and citrus gives structure. A small bottle of grenadine or a bitter red aperitif can help, too. Keep portions small so they stay fresh. Better mixers make ordinary bottles easier to serve well.
Think of mixers as verbs. Soda lengthens. Tonic sharpens. Ginger beer warms. Citrus tightens. Bitters season. Once you understand those jobs, the shelf gets smaller and more useful. A bottle of gin can become a gin and tonic, a Tom Collins-style long drink, a citrus spritz, or a non-alcoholic-adjacent build for someone who only wants a splash.
Buy smaller containers when possible. Big bottles of tonic and soda look economical, but they go flat after opening and make the second round worse. Cans or small glass bottles cost more per ounce and waste less. Citrus should be fresh when it is central to the drink; bottled juice is acceptable only when it is a background note or you are batching.
Keep one bitter option on hand. That might be aromatic bitters, a red bitter aperitif, tonic syrup, or a non-alcoholic bitter soda. Bitterness keeps sweet drinks from tasting childish and gives zero-proof drinks more shape. The home bar does not need twenty mixers. It needs four or five that do different jobs.
Further reading: GQ on home bar basics, Allrecipes on mixers and garnishes, and background on mixers in the list of cocktails.
