How to boost my site in google?

Buying good keyword domains is not enough these days. You still need to build trust with good backlinks, useful content, and give Google time to crawl and rank them. The casino niche is very competitive, so indexing and rankings are usually much slower than other niches.

I wouldn't recommend using PBNs, as they're risky and don't provide lasting results. Instead, focus on building high-quality, relevant backlinks and improving your content. Make sure your site's technical SEO and internal linking are solid. Google isn't known to block casino keywords specifically, but the niche is highly competitive and requires stronger trust signals. Keep working on authority and quality for better long-term results.

I do not think the issue is indexing being broken. In most cases, Google is just very strict with gambling content and takes longer to trust new sites.

Your competitor used a classic churn-and-burn loophole that gets instantly nuked. Exact-match domains and stuffed snippets aren't enough anymore.
To actually rank, stop relying on standard GSC and use the Google Indexing API or high-traffic parasite sites (like Reddit) to force-crawl your links. Build footprint-free tiered PBNs instead of blasting your money site directly, and make sure your expired domains fit the gambling niche so you don't trigger the abuse filter.