If you use laterite, treat it like you want to kill it... 6 feet under if possible. That stuff clouds your water like nothing I have ever seen before! However, for a substrate on a budget, this is what I would do...
First I would put a very thin layer of peat moss in the bottom; I got this tip from Rex! I have never used it, but it seems a small amount won't hurt anything but still has some potential to make a difference. Then, I would put a second, thicker layer of half sand half gravel (a handful of medium sized gravel could help too) with laterite and maybe a little bit of peat moss, but only a small amount. The gravel is to prevent compacting and if you use a little bit of a larger size that would preven it even more... Then, you could either top it off with sand or gravel of your choice. A good layer would "seal" in the laterite layer w/out compacting it too much. Hope this helps!
Tank in transition! 55 gallons, hard water.