Another thing you can do, besides wall, is expand your base. Try to put a Town Center up at all key res points (ie. gold & stone piles). This will provide protection for your villagers as well as a place to create villagers.
To improve your econ, keep making villagers. Put farms around all your town centers to be sure to have enough food to create more villagers as well as the troops you will need to keep your opponent off of his/her resources.
If you get good at this, you can have 100 villagers, four or five town centers, and advance to imperial age around 30:00 (using standard settings).
Everyone has the best point, walls are a waste of time and resources unless used at choke points.
Good luck.
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