hello Francisco,
>> configure 20%(Dynamic Ip)of traffic it goes for the first circuit ,and 80% for the secundary line
you cannot achieve this
you can perform load balancing if you add two default static routes with same AD
ip route 0.0.0.0 0.0.0.0 next-hop-ip-link1
ip route 0.0.0.0 0.0.0.0 next-hop-ip-link2
or you can have a primary and a backup path
ip route 0.0.0.0 0.0.0.0 next-hop-ip-link1
ip route 0.0.0.0 0.0.0.0 next-hop-ip-link2 200
in this second case until link1 is up link2 is not used for outbound traffic
Hope to help
Giuseppe