Try EWBF miner and see if something changes.
800 euro is a very limiting budget and you have 2 main choices:
- Build something that can be upgraded (scalability)
- Build something tailored for max performance (most sol/s with 800 euro)
I’ll try to make a solution beetween these two main factors, so here is an idea:
-https://www.amazon.fr/PRIME-B250-PLUS-Chipset-Intel-Socket/dp/B01MTYDZVY/ref=sr_1_8?ie=UTF8&qid=1503210663&sr=8-8&keywords=asus+prime
MB - 93 euro
-https://www.amazon.fr/Intel-BX80662G3900-Processeur-G3900-Socket/dp/B019XJOYKK/ref=sr_1_1?ie=UTF8&qid=1503210975&sr=8-1&keywords=intel+celeron+g3900
CPU - 48 euro
-https://www.amazon.fr/Clé-USB-SanDisk-Cruzer-Blade/dp/B002U1ZBG0/ref=sr_1_7?s=computers&ie=UTF8&qid=1503211847&sr=1-7&keywords=usb+16gb
USB for OS - 9 euro
-https://www.amazon.fr/Corsair-CMV4GX4M1A2133C15-2133Mhz-Mémoire-ordinateur/dp/B00SV7IIOE/ref=sr_1_1?ie=UTF8&qid=1503211001&sr=8-1&keywords=ram+4+gb+ddr4
RAM - 37 euro
-https://www.amazon.fr/EVGA-210-GQ-1000-V2-Alimentation-PC-1000/dp/B017NW4L6Q/ref=sr_1_2?ie=UTF8&qid=1503211167&sr=8-2&keywords=psu+1000w
PSU - 180 euro
-https://www.amazon.fr/Gigabyte-GV-N105TOC-4GD-4719331339289/dp/B01MEHGRMS/ref=sr_1_1?s=computers&ie=UTF8&qid=1503211544&sr=1-1&keywords=1050ti
2x GPU - 350 euro
Total: 717 euro
You still got 92 euro for risers (you can find them on amazon), i suggest cryptomined from china (high and solid quality products)
-https://www.cryptomined.com/index.php?main_page=product_info&products_id=200:437014d17706f367fdcf9527d186d739&zenid=os0bk13sn378hlq6dp5l59qp73
4x risers 6 PIN - 45 euro (31$ risers + 15$ shipping in europe)
Grand total: 762 euro
You still got 38 euro for any spare parts/rig/keyboad/etc.
So with this system you would get 340 sol/s for 180W:

That’s 30$ profit a month (55$ income - electric cost)
So, with this solution you’ve got some scalability, the MotherBoard can support at least 4 GPU, maybe even 5.
With a little future investment (350 euro) you can add 2 more 1050ti and get:

75$ profit (115$ - eletricity)
After this you can start buying more serious cards and selling the 1050ti for 100 euro (even in 8 months) so you can upgrade sol/s. Would suggest after 1050ti-> 1070 and then -> 1080ti (or newer card).
Upgrading gpu’s you should expect adding a 1000W for the 1070’s and two 1000W for the 1080ti’s.
Oh yeah, for mining i would install simplemining on the usb drive (2$ a month subscription, really easy to implement). BIOS settings are fundamental for successful mining rig.
Cheers mate!