The first thing to do after registering IBKR is to go to

Settings -> Account Settings -> All Account Settings -> IBKR Pricing Plan

Change “Fixed” to “Tiered”
With the fixed plan, commissions for US stocks start from $1; with the tiered plan, commissions start from $0.35
When you place a single order of more than 150 shares, only then does the fixed plan have a price advantage
But if you’re buying, say, $NVDA 150 shares, it’s already $30000—so for us small retail investors, the tiered plan is still more cost-effective