@Dyl linked my thread. Thank you for that.
There you will find some helpful points.
Apart from that I can tell you that there a definitely deals to find. But you can not just go to Akihabara and except to find them. You have to be willing to go to smaller cities/ shops. And focus not on hype or waifu cards since they are always overpriced.
Oh and always check the back of the cards. Most cards had an incredible clean front but the backside was often very worn.
But if you just want to buy some set cards from the past 1-3 sets you will find good prices in most shops if you are not going for the chase cards there.
In this thread I summarized my purchases with prices and gave some advice about what to expect when going to shops in Japan. Maybe this helps as well:
Let me know if you’ve got other questions 