Hello,
It will work without IBGP.
But if You are interested in best practices, then, on a very high level :
1/ Your IGP should ideally contain only loopbacks, less ideally loopbacks+link subnets
2/ Your customer routes should be in IBGP
3/ You should advertise Your summarized customer routes and Your own summarized infra routes (DNS subnets, company portal, etc) over EBGP to the outside world.
Anything else is good for lab practicing/exam prep only.
HTH
Thx
Alex