Lemon juice provides only citric acid, so it can substitute for acid blend but it won't be the same. Acid blend contains tartaric, malic, and citric acids, each of which contributes different flavor.
Tea is a good source of tannin and it is a possible substitute, but it also won't provide the same flavor/effect as something like Scott Labs FT Blanc Soft, or oak. Raisins can also add tannins (along with sugar and flavor).
These additives are all really inexpensive (at least here in the US) and even with all of them you still save a fortune making your own wine instead of buying an equal quantity of commercial wine.
It may seem like a lot all at once though when you're starting, so I understand that.
Hope this helps.