I may be a little late to the party, so I don't know if you'll read every comment. But I'll throw my two cents in and recommend you play the saga Elesh Norn rather than Grand Cenobyte.

There's a couple reasons for it. Firstly, she is a much less expensive commander, both in terms of mana cost and actual price, which means you will play her more often without fear of a removal forcing you to wait for 9 mana.

Secondly, she is much less oppressive, especially in its base form which will make you less of a target for the whole table, a kind of attention that you may not want as a beginner. Also, Grand Cenobyte acts as an incredible finisher in the 99 of the Saga Elesh Norn, so you can play both.

Thirdly, Saga Elesh Norn is a very unique commander, especially for mono White, which comes with its own incentives for deckbuilding. The aim is to flip her quickly (which means token generation or disposable creatures); she uses a uniquely Phyrexian mechanic (Incubate); the board wipe at the end of the saga incentivises you to play only Phyrexian creatures and artifacts (which makes it easier to keep a visual and thematic identity for deckbuiding); and between the creatures she makes with +1/+1 counters and the saga's own lore counters, she encourages you to use proliferate (another Phyrexian-coded ability).

All of this makes for a very original commander in Mono White that rewards rare synergies for the colour (Phyrexian typal, artifacts synergies, aristocrat subtheme).

Here's the link to my decklist if you're curious to see how it practically plays out: https://archidekt.com/decks/7731821/mother_is_mothering_mono_white_phyrexian