This is the main Ibara strategy thread here:
http://shmups.system11.org/viewtopic.php?t=7667
It is a bit long though and you may need to go through the hi score thread also, as it has some good strategy discussion in parts. A short answer is that you need to be bombing more during stage 1.
Bombing not only gets you more points for killing things, it also makes flying enemies drop much more stuff which lets you max out your medals quickly and then score better. Good players can get the medal value at maximum before the first large building that needs to be bombed for tons of medals on stage 1. When bombing in stage 1 try and follow a route through the stage that keeps you constantly picking up bomb fragments so that you can keep bombing, the little tanks are the ones that drop them IIRC.
Once you get to the boss, do a double suicide (one at the busy rotating spam attack and one at the final sword spread is convenient) and you can go into stage 2 with a full bomb to use at the start on the 2 waves of popcorn enemies. Hope this helps a bit - and watch Gakidou's replay which can be found in the hi score thread, it's excellent.
EDIT: That replay is actually in the old hi score thread here:
http://shmups.system11.org/viewtopic.ph ... &start=450
It's also the old hi score thread that has good strategy discussion and most of the topics in the strategy index for Ibara have some useful bits of knowledge in them. Unfortunately there isn't a thread that has collected everything together.