I have a fixture from Aquatraders (yes, you will hear both good things and bad about them) that is 36" with 2 high output flourescent bulbs (T5HO). I have corals and a clam thriving under it in my 12 long reef tank. It's only $50 with free shipping. I've never had a problem with it!
Here's one suitable for freshwater:
Once again, people like to bash these and recommend a fixture that's $200-$300. I'm on a budget and you're on a budget and this light works just fine
It'll provide the coverage you need all the way across the tank.
I personally don't like purply bulbs - I had a pink one in my Coralife and I hated it. You may want more of a crisper, white looking color to your tank. The "kelvin" or color temp of the bulb will tell you what color the light will be - 6500k is yellow-y, which some don't like (me included) and when you get towards 8k to 10k, the light gets more white. 15k on up will give a more blue look, but they are more suited for reef tanks.
Regarding fish, some easy centerpiece ones that get a nice size are gouramis - there's so many different kinds. You could get a pair of pearls maybe (I'm partial to them
but it's your choice! I wouldn't get blues - I always have had a pair fight, but alone they're ok. But, they are considered semi-agressive. And, they're not shrimp-friendly.
If you want shrimp, that will reallllly narrow your choice of fish down. Many here have shrimp-only tanks. I have had neon tetras with shrimp and no issues, while others would'nt even add them!
As schooling fish, cardinals would complement gouramis - any tetra would, or you could go with barbs, but they can be more aggressive (I have an Odessa barb that needs to go because she's chasing my Congo tetras! - even in a school, they always picked on each other).
German blue rams or kribensis would make for a nice pair in your tank - but they are also-semi-aggressive. I have a semi-aggressive community tank with an angel, gourami, some cardinals, congo tetras and they're fine. You'd think their being semi-aggressive would cause issues, but as long as I don't get another blue gourami and add angels the size of the one I currently have, there will be no issues - don't be afraid of semi-aggressive fish
Angels like taller tanks and taller plants, so they may not be a good choice since the 40b isn't very tall, then again, my angel is always out and never in his plants, so who knows?
More peaceful fish would be guppies, platies and mollies, but they are livebearers - something to consider. Cory catfish get along with just about anything, so no worries there, and they like to be in groups.
Best of luck to you - choosing fish is the fun part - if you have any questions about compatibility, feel free to ask us
I've never had a sump for my 55, but I know plenty of others have them, so they can chime in here. Also, I've never used fancy gravel - just the plain stuff from Petsmart for many many years, and have no problem growing plants. Eco-complete is nice stuff, you could try mixing it with plain black pet store gravel to make it go farther. One 10-15lb bag should do it since you already have 40lbs.
CO2 is a choice you may make - but I've never used it - it can be pricy to set up initially. Yes, you will be able to grow a carpet in the front and sustain other hard-to-grow plants, but some of us like to keep things simple (and cheap!). There's many plants you can grow without it, it's up to you if you think it's worth it!
40breeders are an awesome size, not too tall, with a nice depth. Aquascaping that will be fun. Good luck