As we all probably know Bloodstone is a core item on Leshrac, It gives him every thing he could possibly want. I however, am not a big fan of bloodstone. My idea makes his core item build more expensive, but provide more overall.
My idea is that you can get your boots of choice---> Orchid Malevolence----> Rod of Atos. This increases his core item cost by ~2000 gold, but gives him mana, int, attack speed, mana regen, a silence, and a slow. The actives of these two items make a lot of sense to me for Leshrac. The silence is great utility in fights, and the slow is a great set up into his stun. He is also able to make good use of the extra damage from the silence because of his large amounts of damage.
What do you guys think?
Essentially a level 1 Pulse Nova with Aghs is the same DPS as a level 3 Pulse Nova without Aghs FOR ONLY 1/3 OF THE MANA COST.
So you can leave your ult at level 1, and you have an extremely mana-efficient farming/pushing skill that allows you to just walk around and melt creeps.
This is why Bloodstone tends to be popular on him - it's very efficient at providing HP/mana, and right click isn't really an issue when almost all your damage output is magical. However, I'm also a big fan of Rod of Atos as it's cheap, provides a good slow (easy to setup stuns) and lots of hp/mana for the cost.
I think ideally you want a Black King Bar so you can really get in there and get stuck in. Ghost Scepter it very handy here too (doesn't stop you casting). Eul's I do like, but it tends to leave him a bit squishy.
Orchid Malevolence tends to work best for right click heroes, I'd rather get a Rod or Sheepstick instead.
If you're looking for a really cost effective build, try Rod of Atos/ Soul Booster/ Ghost Scepter (you don't have to complete it into BS, and can use the mana booster for your boots for a while), then round off with a BKB or Agh's.
That's 325 + 450 + 133 = 908 hp
325 + 400 + 91 = 816 mana
For 3100 + 3300 + 1600 = 8000 gold
You can slow enemies strongly and become physically immune, plus plenty of regen.
The Orchid on Leshrac is just wasted money, it's like picking it up on Death Prophet. On such Heroes you not only need mana regen, but also survivability: that's why the Bloodstone is so popular (even though it's not the best choice). Other good choices would be cheap mid-game pickups that add mana or mana regen like Drum of Endurance, Rod of Atos (as suggested by you) and - as said before - the Eul's, followed by a big item that bulks up your stats like Aghanim's Scepter, Scythe of Vyse or even Heart of Tarrasque.
I haven't played core Leshrac in a long time, but if I had to play him nowadays I'd probably go Phase Boots into Eul's and Agh's, with optional Drums before the Eul's. My most standard late game choices are, obviously, Scythe of Vyse and Shiva's Guard, along with Heart of Tarrasque, Linken's Sphere and especially Black King Bar versus certain lineups.
I used to play a lot of Leshrac in Dota1 and i used to run in as a position 1. (i know i know completely stupid)
BUT
My build was go MID
early game.
Bottle - cause im mid ...duuuhhh
Arcane Boots - mana mana mana
Mid game
Rod of Atos - the slow plsu the hp and mana mana mana
Black King Bar - you cant stop me now!!
Late Game
Aghanims Scepter - melt puny mortals MMEEELLLLLLTTTT!!!!
Scythe of Vyse - the active helps with chasing and Zoning.
EXPLANATION :
at level 16 i could outlay over 400 damage a second in an AoE of 450.
with bkb i waded into fights and just melted people.
your idea of Orchid though ... i never thought of, mana regen and the silence with damage amp would work absolute wonders.
the attack speed he doesnt really need as he isnt right click.