I'm pretty curious with this, say after the Anschluss or the takeover of Czechoslovakia or after the various invasions in 1940s. What happened to the heaps of gold reserves and other financial assets those countries have? Did they just get 'acquired' by Germany during the occupation process?
Lastly if they did get acquired, how significant were the amount?
I base part of this answer on an earlier one on German pre-war and war spending here.
Most countries had a cold reserve, a reserve of hard currency and other items and would store it at a central bank. They often also had assets at foreign banks, especially if they had a lot of trade with those countries. Several countries moved a lot of their gold to British or US banks before the war for safekeeping and trade - some managed to evacuate it under adventerous circumstances. For example, Norway had labourers carry the gold to sleds to transport it to a hastily mobilised fleet of trucks, which sped north pursued by German paratroopers. The Royal Guard had to make a stand to fend of the paratroopers and protect the gold, the government, the parliament and the king.
The nazis burned through the German gold and currency reserve and all assets seized from Jews and other 'undesirables' and defaulted on all foreign loans in 1939. During 1936, the German gold reserve fell from $33 133 000 to $26 707 000, despite all schemes (MEFO bills) and siezed assets. The nazis printed a lot of money and pegged it to gold in theory, but refused to exchange it for gold, which meant that their reichsmark was only accepted in Germany - they had to pay for all their imports in gold, hard currency (usually British pounds or US dollars) or industrial products.
The Germans seized the Austrian gold reserve in March 1938, yet at the end of 1938, Hjalmar Schacht reported to Hitler that all currency and gold reserves had been exhausted, that 6 billion MEFO bills could not be honoured by the government and that re-armament would have to be cut by 20-30%, or Germany was bankrupt. Hitler, not satisfied with this, promptly sacked Schacht in Januari 1939.
The Czechoslovak gold reserve was siezed in 1939, and parts were delivered to the nazis from the Bank of England, where the Czechoslovaks had sent it for safekeeping and trade, in April-September 1939. The nazis also took over the Free State of Danzig's gold reserve in September 1939, and plundered sizable amounts of gold from the central banks of Belgium and Netherlands.
The Germans set the exchange rate of the reichsmark at about three times as high towards the French Franc as it had been 1930 and thus plundered the French economy (German soldiers and companies were amazed at what prices the German occupation forced the French traders and merchants to sell them French goods) systematically. They did the same in Belgium and the Netherlands.
To total things, stolen gold (all numbers are in 1938 US gold dollars, 35 dollars per troy ounce):
Austria and Czechoslovakia: $146 000 000 in gold.
Free State of Danzig: $4 000 000 in gold.
Poland: The gold was evacuated through Romania, Turkey and Lebanon to France and then to French West Africa and then to the USA.
Denmark: Had almost all their gold in Britain and USA.
Norway: Managed to evacuate their gold to Britain.
The Netherlands: $163 000 000 in gold.
Belgium: $269 000 000 in gold. This gold was, like the Polish evacuated to Dakar, but were delivered to Germany 1940-42.
Luxembourg: $4 857 832 in gold, evacuated to France and taken in the port of Marseilles, awaiting transport.
Yugoslavia: $69 000 000 in gold.
Greece: $28 000 000 in gold (it is hard to confirm that this really was seized by the Germans, but some sources indicate it).
In addition to this, Germany took over the administration of the gold reserves of Slovakia, Bulgaria, Hungary and Romania, a total of $200 000 000, of which none of those countries ever saw any of again.
In addition, the occupied countries were forced to pay for their own occupation in manufactured goods and other assets, a total of $33 735 000 were siezed this way.
Sources: