Leshrac is underestimated on the basis that not many people play him and most of them play him badly. firstly your prefered laning buddies is someone melle and wont ditch you early.
you want your diabolic edict maxed asap because anyone can be killed with it. next and alot of people disagree with this you want to max your lighting storm because whenever you use it it is a great KS move but late game it because useless. my problem with split earth is that timing is very difficult because it takes too long to administer the stun but in ganks and while heros are distract it is good for initiations. as soon as pulse nova can be leveled get it because it does insane amounts of dmage and can be turned on and off when you want but pay attention to the mana loss because it costs60 mana a second when maxed out ( aghanims sceptre is a definite purchase ) when ganking turn on your diabolic and use lightning if any hero is running away with low life and but as soon as anyone comes near you late game flick on the pulse nova and hope to god its not huskar attacking you because who ever you are husky is a B****.
concerning items get phase boots and a magic stick for your mana. once you have these start saving for a blood stone it will take a while but with the right farming it wont take long. after that by what you wish. preferably a aghanims sceptre or scythe of vyse. thats all for items that you really need. u may want a mekanism for your team but dont but it unless necasary.
thats all for now and just remember the basic rules of hero picking if you cant play him well play bots until you can.
bye for now