I commute daily and I was finding that my ears were ringing after every journey, I bought a trial pack from LucyDellEarplugs and it had 20 or so of their most popular ones. I tried each pair for a week (unless they were instantly bad) and kept notes. I then narrowed them down to a couple and wore them a day at a time before choosing the right pair for me, then bought a job lot, think it's was £10 for 50, I use a new pair each week.
I wouldn't ride without them, they cut out all the high end engine noise, I mainly just hear my exhaust, so I know how the engine is revving. If I ride without them it sounds like my engine is falling apart LOL