You will need a motherboard that is compatible with your current CPU and the RAM that you specified (DDR3, I'm assuming?).
Unfortunately, there are likely no dedicated mining motherboards available for that line of processors, so if you're adamant about making use of that processor, you'd need to search more on your own for one that has many PCIe slots.
To a certain extent, your CPU performance isn't a huge deal. Any relatively recent Pentium or Celeron can usually do the job, so your old i3 should be fine. (With systems with very high numbers of GPUs, CPU/chipset limitations with PCIe lanes can become a problem, but that shouldn't be a problem for you.) Otherwise, your CPU performance is only a concern if it's so slow that it can't run the OS/mining software effectively. (Assuming you're only GPU mining and not trying to CPU mine.)
As others have mentioned, you almost definitely will not need a PCIe network adapter card. There are few motherboards that do not already have an integrated ethernet adapter that will work fine for mining purposes.
As far as graphics cards are concerned, it depends on what you pay for electricity and what your PSU can support. Older cards, such as HD 7000 series cards and the R7/R9 200 and 300 series cards, require more power for their hashrate, but can usually be found for cheaper than newer cards. The RX 470/480 cards are better for efficiency and also give good performance on ETH. The 570/580 cards aren't a big improvement over them, and tend to require more power.
Nvidia cards are usually a good choice for equihash coins (ETH is still sometimes better), so I'd consider a 1080ti, 1070, or 1060. The 3GB 1060 probably gets you the best individual hashes/watt (if you do some deal hunting), but you lose out on rig density. (I.e. With a fixed number of slots available on your motherboard, filling them with 1080ti cards gives you more hashpower than 1060s, and if you wanted to use 1060s to achieve a comparable hashrate, you'd have to purchase an additional mobo/cpu/ram/etc. to run another rig.)
As always, nobody here is responsible should you take our advice and dislike the results.
Unfortunately, there are likely no dedicated mining motherboards available for that line of processors, so if you're adamant about making use of that processor, you'd need to search more on your own for one that has many PCIe slots.
To a certain extent, your CPU performance isn't a huge deal. Any relatively recent Pentium or Celeron can usually do the job, so your old i3 should be fine. (With systems with very high numbers of GPUs, CPU/chipset limitations with PCIe lanes can become a problem, but that shouldn't be a problem for you.) Otherwise, your CPU performance is only a concern if it's so slow that it can't run the OS/mining software effectively. (Assuming you're only GPU mining and not trying to CPU mine.)
As others have mentioned, you almost definitely will not need a PCIe network adapter card. There are few motherboards that do not already have an integrated ethernet adapter that will work fine for mining purposes.
As far as graphics cards are concerned, it depends on what you pay for electricity and what your PSU can support. Older cards, such as HD 7000 series cards and the R7/R9 200 and 300 series cards, require more power for their hashrate, but can usually be found for cheaper than newer cards. The RX 470/480 cards are better for efficiency and also give good performance on ETH. The 570/580 cards aren't a big improvement over them, and tend to require more power.
Nvidia cards are usually a good choice for equihash coins (ETH is still sometimes better), so I'd consider a 1080ti, 1070, or 1060. The 3GB 1060 probably gets you the best individual hashes/watt (if you do some deal hunting), but you lose out on rig density. (I.e. With a fixed number of slots available on your motherboard, filling them with 1080ti cards gives you more hashpower than 1060s, and if you wanted to use 1060s to achieve a comparable hashrate, you'd have to purchase an additional mobo/cpu/ram/etc. to run another rig.)
As always, nobody here is responsible should you take our advice and dislike the results.
One question; Should i attach a SATA power cable to my hard drive as well as a SATA cable connecting the hard drive to the motherboard?
A SATA hard drive requires both a power connection the PSU and a thinner connector that goes to the motherboard for data.
