Learn Italian: Evitare tutto ciò è sempre ragionevole. - Avoiding all that is always reasonable.

ciò is an invariable pronoun (it never changes its ending) used to refer to an abstract concept, an idea, or a whole situation, rather than a specific physical object. You could actually say tutto quello here, but tutto ciò is a very natural and common way to say 'all of that' or 'all this' when talking about situations.

Why isn't there a translation for 'of' in tutto ciò (all of that)?

In English we often say 'all of that', but in Italian, tutto attaches directly to the pronoun without needing a preposition like di (of). You just say tutto ciò (literally: all that).

Why is the infinitive evitare used to mean 'avoiding' instead of the gerund evitando?

In Italian, when a verb is the subject of a sentence (the thing being 'reasonable'), you must use the infinitive form. The Italian gerund (words ending in -ndo) is strictly used to show an action in progress, like in sto evitando (I am avoiding), never as a noun.

Since ragionevole describes an action (evitare), what gender does it take?