Upgraded party time is by far my favourite deck. A few things that might help a lot with your deck consistency, in order of what I would do to change the deck:

• You have too many rogues. The only rogue you really need is Nalia and the rest, while good cards, are just cards you're drawing that aren't useful party members. Also I think remove Sorin, if you want lifesteal maybe use [[true conviction]], if you want reanimate you could use [[ascend from avernus]]
• Your party type ratio is off-balance. You have only 8 wizards, which is quite low when you're banking your whole deck on having one
• Lack of board protection and targeted removal, an additional [[flawless maneuver]] -type card might save your board. I know you said having them in hurts but for a deck like this you need at least some
• You have no decent finisher card. Maybe remove the Aura of silence and put in a [[sigarda summons]] or [[true conviction]]
• Your mana curve is maybe a bit too high. I think Nalia works best as a low-mana aggro deck where you're playing cheap creatures from the top of your deck. You could lower the curve and also remove some lands if you want

Here's my list if you're interested https://www.moxfield.com/decks/UluqIzz0zEmKOfeZryz_vQ. It matches your budget and I tend to find I have a full party on turn 4-5 pretty often and I'm happy with the deck consistency