For getting live market price data for SPX and SPX options, the following market data subscriptions are required:

• US Securities Snapshot and Futures Value Bundle $10/Month (Waived if monthly commissions reach 30 USD)
• US Equity and Options Add-On Streaming Bundle $4.50/Month

Interactive Brokers requires you to have funded your account (typically with a minimum of $500 plus enough to cover market data fees) before you're able to see realtime data.