A progression of adjectives related to size would be: small, tiny, teensy — "teensy" being even smaller than "tiny". Note that teensy would never be used in formal writing. Another example is cutesy. However, this morphological change is not a generalizable production.

In English we have the suffix "-ish", which can be aplied to many, but not all adjectives. It means "like that, but not so much", so in a way it is diminutive. for example:

smallish, greenish, mannish, etc.

It would generally be understood this way if you coined an uncommon word with {adjective}+ -ish (say it with a distinct pause at the hyphen, so they can tell you know it's not a standardized word); For example:

funny-ish, clumsy-ish, huge-ish, cold-ish, round-ish, square-ish, young-ish

(there's a comedy on American TV called Black-ish)

but -ish can also mean "like that" (and not just a little bit) when attached to a few nouns: oafish, childish, churlish, foolish, foppish, rakish.

Or "a person or dialect from there": British, Swedish, Polish, Spanish

I would say if you want to express a lesser degree of an adjective you say: a bit expensive, not very useful, little helpful, rather small. You don't do it by adding suffixes.