it all depends on your tank. Personally, the tried and true are astraea snails (not the turbos unless you have really bad hair algae-like covered rocks or outbreaks) and nassarius (vibex or tonga variety). Ive had many many things in the past that have all served a purpose (money cowries, slugs, urchins, crabs, shrimp) but the best right off the bat are gonna be astraea and nassarius. note that if you run with no sand, do not get nassarius. theyre sand digging guys.
That being said, if i were to do a big tank, I would get a sump for it. I run a 40 without a sump and its not hard but lots of water changes. With the 40, i have a reef octopus hob skimmer with a filter sock on the outbound with chemipure elite in it. I also have a gyre wavemaker and two other offbrand pumps for flow. It is my grow out so lots of nutrients going into that tank and lots of fish poo too lol
If youre only going to have a pair of clowns and some easy corals, my advice would be the following:
1. no need for a skimmer. there will be such a small bioload of 2 clowns in 46 gallons that you dont need that heavy nutrient export.
2. get plenty of flow in there. Im partial to the hydor coralia circulation pumps. This serves as flow for corals as well as getting food and poo up off the sand/ground so it can be picked up by filtration.
3. Filtration. I would get 2 hob filters (like the marineland big ones). Buy a big pack of white and blue filter floss on
amazon, the ones you can cut to size. That will be your main gunk getter outer. I would also run the correct amount of chemipure BLUE for the tank size. the blue has activated carbon, gfo (a great work around for a skimmer for sumpless tanks), and beads for clarity.
4. basics like rock, sand, thermometer, heater, etc. I love the cobalt line of heaters. you can set it to what you want and forget about it for the most part.
5. lighting. EVERYone has different opinions on this but i really like the AI prime HDs. I have 2 over my grow out 40 gal breeder and theyre wonderful. super user friendly and easily pulled up to edit on your phone. I cant for the life of me grow sps in my tanks though so i cant speak for AI prime growing ability for those.
this would be how I would do it because I dont have hundreds to spend on sumps/skimmers/fancy lights. If you do, there are SO many options out there. Biggest piece of advice is do your own research and tons of it. If you know what you want, keep researching. BRS TV has great mini series that detail pumps, tanks, fish, cleaners, you name it.