Hello my friend.
If you already decided to start mining with GPU system, go ahead then but I have to tell you that it could be better and more profitable if you get an antminer S9 (at a good price logically).
Well, for a mining rig, i recommend to you the following components:

Mother board: https://www.asrock.com/MB/Intel/H110%20Pro%20BTC+/index.asp
Power supply: https://www.pccomponentes.com/evga-supernova-g2-1300w-80-plus-gold-modular
GPU: RX570 4gb or 8gb
RAM: For only 6 GPUs, (4 gb) if you are gonna add more gpus until 13, just 8gb ram
Micro: Intel celeron basic compatible with the mother board.
Risers: https://www.amazon.com/MintCell-6-Pack-Powered-Adapter-Extension/dp/B01GU94QSQ/ref=pd_sim_147_3?_encoding=UTF8&psc=1&refRID=QZ7SJC2ZC32BPZ847KA4
USB: Kingston 16Gb (SMOS) or a SDD (Windows)
Rig structure: by yourself


Thats my opinion. If you want an extra help, just reply to me the message or just contact via pm.

Regards and good luck.

You sound like you live close to me with your cost.  I would recommend 1070ti 6 card rig or a mix and match of 1070 and 170tis based on the availability of cards.  You can put together a rig for 5k with no issue.  The guide below I wrote will get you to 6 cards 1070 or 1070ti for right around 5k depending on the availability of the hardware which can be tricky.  If you have any questions I would be happy to help.


https://theminerhub.com/mining/building-a-mining-rig-part-2-hardware