So your budget is pretty much US$360 (260 Eu) or below.

If it HAS to be brand new:
1) The OnePlus One (no microSD) is only $349 for 64GB.
2) For 32GB its $299, but availability is "nonexsistant" for both.
The Nexus 5 (16GB) is 290 Euros in Greece, close enough to your budget.
The Moto G (16GB) can be had for ~$290.

If it does NOT have to be new:

3) Best to grab a "used but new" Nexus 5 (32GB).
From ebay its ~$270, add shipping with insurance... so that's ~$300.
4) Or even The Moto X (16GB) off ebay for ONLY $190
5) Used Moto X (32GB) goes for $260 (add ~$30 for international shipping and insurance).
6) A used Note 3 can go as little as $370, just think about it... its the best phone on the market.
7) SONY Z1 Compact is a very desirable device, but a lil dearer at $440 used

...those should be the first on your list. Since you want to dabble with coding a bit and want to even try making a game, I'd suggest Android first... iOS is not as "free".

But if you really want a TABLET, like I said:
Number 1) 32GB Wifi Black iPad Mini Retina (hands down king) - $400 (used) or $470 (new) + p/h
Number 2) iPad Air (for some reason the Mini really impresses me) - $490 (used) or $540 (new) + p/h
Number 3) iPad 4 (32GB Wifi Black) - $300 (used) or $490 (new) + p/h
...
...
...
Closing words:
Buy from ebay. Use PayPal. Get Shipping insurance (€22). Buy a used device. Shop aggressively.
Choose between the €195 Nexus 5 (32GB) or €215 iPad 4 (Wifi 32GB)... otherwise get more funds.

I'd be personally disappointed if you didn't get one of those two, but the other options I listed above are good too.