Making an engagement ring. Where are the headaches?

Hello,
Im on the path of making an engagement ring for my soon to be wife.
I have never made anything this small, but I am handy. I've been working on bikes for many years and I've got a workshop.
I've also done most of my homework and I got sort of a plan, but I need you help on where am I going to go wrong as a first timer, plus some side questions.
Here is the idea.
I already have an idea of what would it look like - a simple ring with a stone on top of it, 4 prongs, no flowers, no nothing more.
I am able to carve the model in wax, but I am unable to cast it with the lost wax casting method, however I am going to be able to cast it in delft clay, and if it fails - I still have my wax model to try again untill I get it right.
That is the basic idea.
Im not really sure what material to use - silver or platinum. Silver would be cheaper I think and much more doable, considering the melting points.
After the cast I will grind it with a rotary tool I have in my shop, then polish. I've seen alot of videos about it on youtube.

Where am I going to slip up and fail miserably?
Thanks in advance.

I would possibly make it from wire etc depending on your design. Casting can be a pain if you haven't done it before. Platinum especially so, you will need a lot of metal to use delft cast method which would get very expensive very quickly in PT and an oxy-acetylene torch to melt it. I'm not even sure if delft would take the temps required. Casting houses can cast the wax for you. If you send them your model .If It took a long time to carve I would get a rtv mould made so you can get copys done if it all goes wrong . Then all you would need to finish and set the stone. Also pay attention to the size of the claws you make they dont want to be to thin or too heavy and an under bezel so the stone sits more secure.

Thank you for your reply.
I am still considering the material and I might go with silver, which would be much easier to cast in delft clay.
I dont want to outsource stuff because it defeats the purpose of me making it. I plan on filming the whole process for a proposal video.

Wire method might work aswell, but I dont have much equipment. Matter of fact close to none. I will buy the torch, pots, materials and some other tools but mills and such for just one piece is not worth it. Thats why im going with the delft clay casting.

Ah cool that's a nice idea, Silver is easier you can melt it with a plumbers torch. You will need to make the claws a bit heavier in silver as its quite soft as a material. You may need to drill a hole in the side of the delft rings and cast it on its side with the ring upside down to do it in one piece. You can reuse the sand so deffo have a couple of practices first. I would allow half a size up for shrinkage but you can dial that in after a couple of goes.

As you seem to be going for white metal and went to the 2 extremes in cost have you thought about white gold as it’s an engagement ring?
Why would you need a mill when you can buy the exact amount of sheet and wire in the dimensions that you need? You will need tools even for the basic clean up of a casting and setting tools etc.
It’s not really defeating the purpose if you have designed and carved your design and decide to have it professionally cast. You will still need to finesse the casting, set the stone and polish, which for a first time would be a great achievement . I’m sure your girlfriend would be impressed!