China should have started spending at least twice that on defence from 20 years ago. To start now it's simply too late. The pressing issue would have been to reduce the gap in strategic systems, nukes and SSBNs so that any ideas of the US somehow surviving relatively unscathed in a nuclear war against China would have been completely burried. Additional tactical and power projection assets would have been useful too (more modern planes, carriers etc.), but that is secondary to guaranteed MAD.
China started our military buildup later with 3 advantages:
1. It made us look unthreatening for as long as possible, which is the opposite of what the Soviets did. It allowed us to milk the US/West for money and technological cooperations when we were still weak and needed them. They weren't scared and thought we didn't even have MAD in place.
2. It prevents a buildup of legacy systems especially when Chinese military tech is moving so fast. At a time when Chinese military machines were qualitatively worse than their American counterparts, building a horde of them meant higher maintenance for things that because quickly obsolete. Waiting for technological parity or superiority to build in mass means you will eventually have a leaner, more effective force.
3. Economy and tech grow in a snowballing fashion, so the more you could put into it (and not invest into the military) at early points, the faster the snowball builds and the faster you get past the point where the West could still suppress China.
The danger to this would have been if the US realized too quickly and attempted to pull a Thucydides' trap before we were prepared. But that window is closed now because the instant China sensed hostile competition with the US, we quickly and heavily built up our nuclear forces with modern and advanced missiles, to prevent American adventurism.