darllen
Dw i’n hoffi darllen. Ffantasi drefol ydy fy hoff ffuglen. Mae hi'n debyg i ffantasi uchel, ond mae hi mewn dinas gyfoes. Dw i’n hoffi ogystal darllen nad ffuglen llyfrau ffeithiol hefyd, parthed ynghylch ieithyddiaeth, ceir, ac yr ocwlt.
<em>Ffantasi</em> can be either masculine or feminine, so <em>mae hi</em> is fine, but if it's feminine it will mutate a following adjective (<em>trefol</em> > <em>drefol</em>; likewise <em>cyfoes</em> > <em>gyfoes</em> after feminine <em>dinas</em>). <em>Parthed</em> is literary Welsh, so I changed it to the more colloquial <em>ynghylch</em>. <em>Llyfrau ffeithiol</em> literally means "factual books", it's used for "non-fiction". Apparently "high fantasy" is indeed <em>ffantasi uchel</em>. <em>Yn ogystal â</em> means "as well AS" (<em>ogystal</em> by itself doesn't make much sense), if you just want to say "as well", use <em>hefyd</em>.
Don't worry, it wasn't complete gibberish!