First time blackberry gum auto outdoor

Growth seems to be fine. Hasn't grown much vertically only 4cm. But seems to be gaining a lot of stem thickness and many young leaves are coming out making it bushier. I am still considering a larger pot but not sure if it is necessary. Can anybody tell me if 5l is ok for my plant. I don't need to maximize yield and a super large plant is not needed. Just wondering if a smaller pot (5l) could still harvest a nice healthy plant with a decent yield. I am still using no nutrients and only water. I am really considering buying a booster to help out since my soil might run out of nutrients soon.