If this is a hobby I assume you have another full-time job? If so, then the amount you earn with your 'hobby' will be added on to your existing earnings and taxed at the relevant rate, regardless of whether you are a sole trader or a Ltd. Co.
In other words, if you are already earning up to (or over) the 20% bracket – €35,400 per year – then you will be taxed at 41% on the extra income regardless.
One advantage to having a Ltd. Co. is you can control how much of the extra earnings you pay yourself as an income, and therefore control the amount of tax you pay. However, if you are a one-man operation then this will be of little benefit as you will probably want to take out all earnings before year-end to avoid double-taxation (ie. paying Corporation Tax on profits and then paying Income Tax if you withdraw the money as income later on).
My advice would be to avoid setting-up a Ltd. Co. for a 'hobby' type income.
As suggested, read through the many other threads to get an idea of how this works.