Cool deck! Nekusar's a fun dude, although your friends might find him a bit painful
First off I see you're running a lot of taplands. This is a common mistake for budget decks. You have two options here depending on your budget. First, you could look into some cheap dual lands that have the potential to enter untapped (check lands, battle lands, reveal lands, pain lands). If this is outside your budget I'd recommend replacing at least a few taplands with just basics (specifically remove ones that don't do anything useful, like guildgates). This will allow you to not be constantly a turn behind on mana. I also don't think the Blighted lands are worth running. The effects aren't that great, and since you're in a budget build you need to focus on lands that give colors. Also on this note,
Temple of the False God is probably worth cutting. It's good for decks that can ensure the 5 land requirement quickly, but being outside of green makes that difficult. So since it can be a dead land early and even once it's active it doesn't provide colors, I'd suggest cutting it.
Second, your ramp package is curved a bit high. I'd recommend replacing your more expensive rocks (
Dreamstone Hedron,
Hedron Archive,
Darksteel Ingot,
Commander's Sphere) with ones that cost 2 or less (Talismans, Signets,
Wayfarer's Bauble). This will make you get things going a bit faster with early ramp.
Third, some of your removal options are a bit underwhelming.
Final Death costs too much, and you have a lot of better options in your colors (
Reality Shift,
Pongify,
Terminate,
Crosis's Charm,
Bedevil,
Drown in the Loch). I'm not a huge fan of
Rewind either, except in decks that can specifically abuse it.
Arcane Denial is a great counter for Nekusar. However I like the usage of return to hand removal in combination with wheel effects. Very nice synergy.
Overall you have a pretty nice amount of wheel effects, extra draw effects, and punishment effects. There a few more you could add in if you want (
Jace's Archivist,
Whispering Madness,
Megrim,
Liliana's Caress,
Dictate of Kruphix,
Prosperity,
Molten Psyche,
Temple Bell)
Generally the deck looks pretty good and I think fixing the land base and ramp package would have the biggest impacts on making it play more reliably. One optional thing you could do is incorporate some more recursion effects since you'll be wheeling a lot of stuff into the graveyard. Either creature recursion or spell recursion (
Spelltwine,
Volcanic Vision) could be nice.
Good luck!