Not knowing your level of experience, I'll just offer some suggestions on substrate. I have used pea gravel, fine gravel, play sand, and plant enriched substrates over the 20+ years in this hobby.
First, avoid white. This is not natural and it does impact on fish. I also find it hard to view white-substrate tanks because of the glare; imagine what this does to fish. As for other colours/tones, something "natural" will probably provide more satisfaction long-term. Many use black, and I have once, but I found it was more dull grey than black under the lighting (any substrate when wet and lighted will be different than when dry) and every speck of stuff was very visible. I never see this (except for larger bits of plant leaf or something) with mixed tone sand or gravel.
Second, consider intended fish. If substrate fish like corys or loaches are likely, sand is by far your best substrate. Substrate feeding fish like many of the small to medium-sized cichlids also will be better as they can naturally sift the sand more easily than gravel. With fish that really dig, sand can be more of a nuisance than gravel. Whatever material, make sure it is smooth, meaning not sharp or rough. I had significant damage occur to some corys due to a rough substrate though in my hand I had thought it was OK. Play sand is fine for this, but paver or blasting sand is usually too rough by comparison.
Plants will grow well in sand or fine gravel; some do have more difficulty in larger pea gravel. A finer material (like sand and fine gravel) is also better for the bacteria/organics aspect of a healthy substrate.
I used fine gravel for years, then switched all but one of my tanks over to play sand 2-3 years ago and wish I'd done it sooner. One tank had pea gravel, it now has fine gravel which suites the aquascape better as this is a river habitat with river rock boulders and chunks of wood.
Byron.