It really depends on what you are trying to go for, since aquascaping is more about the art itself and less about trying to optimally grow plants, unless you only want to do iwagumi or dutch where plant growth maters a lot more.
That being said, my vote for any beginner starting on their own has always been sand only substrates with a mix of some humic material, like dead tree leaves or other botanicals. Pool filter sand is the cheapest at 10usd per 50lb bag, or you can go with Black diamond blasting sand for a similar price. (You may have to rinse before hand)
You can boil the leaves first and scatter them on top of the sand, chop them up finely and mix them into the sand, or layer them under the sand with some peatmoss (wet of course). The purpose is to get a nutrient recycling process going in order to create a natural soil substrate that can continue supporting plants without polluting the system.
Sand is inert, and dead tree leaves decay slowly and barely alter the water during its decay while containing most of the needed nutrients that plants need to grow. It will take only a month or so until the broken down nutrients in the sand be ready to start supporting larger root structures for more demanding plants, but most plants don't even require substrate to grow initially. If you stick with a lot of easier stem plants and epiphytes, you can avoid the extensive stabilization phase in the beginning common with bare aquasoils and garden soils and get right to planting and aquascaping.