Nowadays everyone does a Puja with an overwhelming use of akshatas.Akshatas are the substitute for everything starting from the dhyana/avahana mantras to tamboolam(betel leaves) in case you don't have them.
Akshatas:Whole rice grain mixed with a pinch of turmeric(some use kumkumam in place of turmeric) and a little bit of ghee/oil/water(optional).
A typical shodasaupachara Puja of Lord Ganesha is like this:
Here,when we say Mahaganpatim dhyami avahyami, it is understood that we need to sprinkle few akshatas on the idol of Ganesha to install life in the idol which is to remain there till the completion of the Puja.So aksathas replace the use of dhyana/avahana mantras .
Also,when we say asanam samarpayami we also sprinkle akshatas instead of offering an actual asanam(a seat for the Lord).Any of the the 16 upacharas that we don't have in real,we are to offer akshatas in place of each of them.
My question-Who propounded this method of Puja?Was it Adi Shankaracharya?