120 Gallon tank SUBSTRATE HELP!

hi guys really need some urgent help setting up my 120gallon tank.

ok im either using a sump or a canister filter (eheim )

i am thinking of growing GLosso, hairgrass and HC all together in the same thank.

i already have some soil, think its repackaged magicsoil 10kg and 60kg of lapis sand with about 10kg plus of river pebbles.

i understand the need of using expensive soil such as ADA aqua soil and all.

could some kind soul out there set me on a better direction on how to lower the cost of the substrate (buffering by mixing with inert lapis :P)

basically need some help to determine how to do up the substrate.

Thanks for all your help fellow forumers.