I am currently erecting a 2 bedroom flat and the foundation has cost me almost 700k, I personnaly supervised it and was responsible for buying all materials, the structure is standard, but im feeling its on the high side. area is Ikorodu and its a solid land. What do you think, experts. Im I overspending or what.

Breakdown of details will make it easy to let you know where the excess sank to, this will allow for adjustment as you progress.
However, common pitfalls when you try to do it yourself without sharing experience or expertise include the following;

Supplying wrong tonnage of sand/gravel a 5ton tipper can deliver 3.5tons, while 7ton tipper can be described as 10tons
Expensive materials like cement can be over-estimated & excess stolen from site
You may have been overcharged for labour
Your design/size may be unique, meaning 2 different 2br flat may require up to 30% diff in cost etc

Best Regards

you are not overspending, Infact that is an average cost.
since you are supervising it yourself, u would want the best and won't want shortfalls.