What gravel bike should I get on a budget? Decathlon or used?

Hey everyone!

I’m looking to get my first gravel bike and I’m trying to spend as little as possible while still getting something decent and reliable.

I’m based in Germany and my main goal is to do longer rides, probably around 50–100+ km, with a mix of paved roads, bike paths and some gravel/light trails. I’m not looking for anything super fancy or race-oriented.

I also don’t want to buy a cheap bike now and feel like I need to upgrade or replace it after a year or two. I’d rather spend a bit more upfront if necessary and get something that I can ride for several years without feeling the need to upgrade.

A few questions:

Is Decathlon a good option for a budget gravel bike?

What would be the minimum amount of money you’d realistically recommend spending on a new gravel bike?

Are there any specific models/brands I should look out for?

Would you recommend buying used instead? If so, what should I check carefully when inspecting a used gravel bike?

Are there any components or frame issues that should immediately be a red flag when buying used?

What would be a good price range for a used bike that is actually worth buying?

What would you recommend if my priority is buying once and riding it for several years, rather than buying something cheap and upgrading after 2 years?

My budgis fairly limited, so I’m mainly looking for the best value for money, rather than the lightest or most high-end bike.

Any recommendations or things I should avoid would be greatly appreciated!