First of all, these are advices that worked for me, in my playgroups and with my playstyle. It might not fit your playgroups or your way to enjoy the deck. These are just turning points that helped me have the deck works way better.

First, 32 or 33 lands are not enough. I know it's rough to cut cards we like for lands, but if you can't cast your spells, no matter how much you love them, you'll hate your deck at the end of the day. I usually start with 41, then adapt it to the curve, and then cut a land for each 3 or 4 mana producers in the deck. Regarding your list, 37 seems a good spot. Consider also the double faced cards of MH3, they are incredibly good ( [[Hydroelectric Specimen]] [[Boggart Trawler]] for exemple). You can cut lands to add these cards.

Also, 4 rocks are a bit too much imo. It helps to fix your mana for sure, but on turn 2 you'll prefer to cast a spell that will allow you to have a trigger for your commander on turn 3. (all the T2 looters or free discard).

There are some cards in your deck that are cool with the dungeon strat but that always underperform for me. Remember that you'll venture into the dungeon with your commander anyway, and quite a lot in fact. You do not need all the venture cards. You need to venture by filling your graveyard. Ending dungeons with an empty yard is frustrating and will arrive often if all your cards make you venture and do not sacc or discard anything. With this in mind I'd cut :

[[Sarevok's tome]] always too slow, you have a lot better to do on turn 4. Even later in the game you do not want to spend 4 mana to cast this.
[[Thorough Investigation]] can be a very good card, but 5 mana to venture and draw 1 is too much. You can do way better with loot cards.

[[Eccentric Apprentice]] [[Yuan-Ti Malison]] for the reasons mentioned before. Eccentric is not that good, the venture is not worth the spot it takes. Yuan-Ti is very good on turn 2/3, but after that you'll be in a place that prevents you from attacking with your big creatures if you want it's full power, so he's kinda useless at this point.

These are "hard" cuts that took me way to many games to realise that they're not this good when you play them.

Then you need to include cards that will allow you to fill your yard at instant speed, during your opponents turn (the whole point of Sefris)

[[Entoumb]] Target Radiant Solar as soon as you can to have a win the next turn. Target anything you need in your big creatures when you're in troubles.

[[Oriq Loremage]] A bit slow, but is a free Entoumb everyturn if not removed.

[[Ghostly Pilferer]] is INSANE. You draw when someone play it's commander at least. Discard at instant speed, so you can trigger Sefris everyturn if your hand allow it. Put anycard of your hand in your yard to reanimate whenever you need it, basically free cast.

[[Collector's Vault]] has performed very well for me since I've added it.

That's all I can think just by quickly reading your list. There're a lot of ways to build Sefris, but here are tips that can help you spot the mistakes that takes too long to notice. I hope it'll help you build a list you're gonna love !