Step 1. The country creates a law forbidding any financial interactions with "offshore" countries (list is populated manually by lawmakers) and also with companies working with such offshore companies (shell intermediaries) in "good" countries.
Step 2. Country forbids its citizens from owning any assets or be incorporated in the same "offshore" countries.
Step 3. Blanket ban of cryptotokens.
Step 4. Huge inheritance taxes.
Step 5. Incremental tax hikes for second and more houses/apartments owned. Restrictions for corporations owning a lot of residential properties and huge taxation.
Step 6. Ban or restrictions of airbnb-like activities to discourage parking money in the housing market.
Basically look where rich hide money go for that. When they switch tactics you follow.
Step 0. Big independent financial auditor structure, independent from law and judicial branched both (or almost independent). From experience - you can dismantle a lot billionaires even with existing laws, if only someone looked close enough and punished them. This is a huge problem in eastern europe for example.