I sometimes skip my period and during this period I see red dots (small) along with white discharge.

I want to know, do I need to consider this as istehaza and do gusl for it or I should ignore it?

If the bleeding has no continuity, it is istihadha. Istihadha is of 3 kinds, qaleel, mutawassit and katheer. Qaleel does not require ghusl rather before namaz, if the under clothes have gotten najis, they need to be changed, purify the private parts and wudhu needs to be done. Blood of istihadha breaks the wudhu therefore if it comes out before namaz, wudhu needs to be redone along with the above purifications.