There are a lot of specialized tools but also many which are common to all bikes. Good cable cutters are one example. I have never regretted the money I spent decades ago on my Felco cable cutters, they worl like the day I bought them. Hex and Torx keys are another, but you should consider them consumable, to be discarded when worn, although you CAN grind back the tips to expose new, sharp edges and prolong their life.
For my use I stick with older bikes that use the old standards like square taper cranks so I minimize the number of special tools I need to buy.