Earning an average income from direct referrals at cashium works just fine without any upgrade. It helps to upgrade but the difference won't be too big unless you really have a lot of active referrals clicking.
At cashium you rent human referrals and that's why active referrals click 4 ads or more everyday. The system allow people to rent referrals several times and that's why cashium is always having referrals available to rent.
If you want to earn from rented referrals, be sure to upgrade before you start renting referrals. This increase your profits too much to ignore it. Have atleast $50 for a 6 month upgrade and $29 - $58 to rent 100 - 200 referrals else it will slow down your earning speed. In total, that is $108 - $79 for a first investment. You can also add some extra money to that for recycle if you want.
Inactive referrals get auto recycled after 10 days of inactivity. But I recommended that you recycle an inactive referral after 3+ days of inactivity to increase your earnings to the max.
Reinvest your earnings and rent more referrals to increase your earnings to the max! But be sure to have extra money in your account to renew referrals that expire.
I hope this will help a few people out there :)