Z370m D3H or H310-S2H? For gaming and budget

Solution
Z370 motherboards support CPU and memory overclocking (if you have an unlocked K-series chip) and multiple graphics cards.
If you won't be using any of those features then go with the H370 (ASRock H370M Pro4 ) but for gaming you should not go below B360 series.

The B360 have fewer features than H370, but it comes with USB 3.1 ports, Dual channel support and Optane Memory support (MSI B360M PRO-VH )

H310 motherboards are stripped down of many features like PCI-E 3.0 support, only supports single RAM DIMM per channel (reduced bandwidth) less USB and SATA ports are supported and no Intel Optane Memory support (you may want it in the near future)
Z370 motherboards support CPU and memory overclocking (if you have an unlocked K-series chip) and multiple graphics cards.
If you won't be using any of those features then go with the H370 (ASRock H370M Pro4 ) but for gaming you should not go below B360 series.

The B360 have fewer features than H370, but it comes with USB 3.1 ports, Dual channel support and Optane Memory support (MSI B360M PRO-VH )

H310 motherboards are stripped down of many features like PCI-E 3.0 support, only supports single RAM DIMM per channel (reduced bandwidth) less USB and SATA ports are supported and no Intel Optane Memory support (you may want it in the near future)
 
Solution