I’m doing a small batch something like 2.5 gals into the fermenter. I have a liquid yeast I am going to use. Should I bother making a starter or just do a direct pitch? The beer is a 6ish % abv west coast style ale.
I brew 2.5 gallon batches. Starters are by no means necessary (though with that OG, you'll likely be under pitching without one). But regardless, I generally do starters for liquid yeast for a few reasons. It reduces lag time on the beer, it ensures the yeast is viable, and it makes sure I have the proper pitch rate. Definitely use one of the calculators to help you figure out how many cells you need for your particular gravity and how much starter to make, if you go that route.
The other benefit I get from starters is saving yeast. I generally make twice as much starter as I need. I then pitch half the slurry and save the other half in a jar in my fridge for a future batch. That way you get the cost savings of reusing your yeast, but you don't have to worry about hop matter or trub in your slurry. When you brew small batches, doubling your starter this way is a lot simpler.
Generally, I don't worry about a starter for my standard 10 liter batch. Having said that, it also depends upon the OG of the batch, the age of the yeast, and the type of fermentation profile. I will do a starter for a much higher gravity or if the yeast is greater than 4 or 5 months old (depends upon the specific strain. You can also alter the flavor profile with an overpitch or underpitch. I will slightly underpitch a Hefeweizen yeast. Likewise, I will over-pitch a yeast when I want a slightly cleaner profile from that strain.
I have recently started doing some cell counts on new packages of yeast (mainly Wyeast) to validate my previous data regarding viable cells of older packages. In general, because much depends upon the strain, the packages will be over the 100 billion viable cells if within 4 months of the packaging date. With the recent change to 'best by' date, I decided to check the last couple of packages I purchased to confirm my previous work. Easily the packs were well above the 100 billion cells, even the WY12728 which was packaged in July, 2020 and used in October 2020.