You list your location as EU. I don't know what credit cards that give status (or help with status) are available in your country. In the US, you can get Hilton Gold with either an Amex Surpass card ($75/year) or a Citi Reserve card ($95/year), and you can get IHG Platinum with a Chase card ($49/year after the first year, and for that $49 you get an uncapped free night certificate). Then the Marriott card from Chase and the SPG card from Amex give you the equivalent of some elite status night credits, but not enough to get you to a "meaningful" elite status level with just the card. (I don't belong to Hyatt so I'm not sure to what degree the Chase card for Hyatt helps with status there.)

The next thing to keep in mind is that status is typically good for almost two years if (but only if) you earn it soon after the status year turns over. For example, earning status at Hilton in April 2015 means you have that status through March 2017, but earning that same status at Hilton in November 2014 means you only have that status through March 2016. I mention this for Hilton because there's usually a 4-stay-to-qualify-for-Gold promo that can be found on FlyerTalk (though you can only sign up for that once you lose Gold). and that's best to do in April for maximum status length.

Then at Marriott, there's the concept of rollover nights. If you earn 51-74 elite nights, you get Gold, plus 1-24 nights rolled over into the next year. But the third year, you can't re-roll the same rollver nights.

Also, at Marriott you can get 10 status night credits for holding a meeting. That has led to a thread in the Marriott forum about "earn Platinum status in 8 days, $800, no stays needed".

However, ignoring these "tricks", you generally have to requalify with exactly the same number of nights/stays in years 2 and 3 and 4 as you did in year 1. (That's assuming you qualifying the "normal" way in year 1, but several programs have a "trial" status promo which you can only use once, so it's actually easier to qualify your first year with fewer nights, but in your subsequent years you have to do "normal" requalification.)

So, as you can see, there's only a simple "general" answer to your question if you ignore every trick in the book. All the tricks, however, are specific to each hotel program. And furthermore, the tricks may vary (especially the ones related to credit cards) depending on which country you're based in.