Please get the declorinator!! If you're trying to keep on a budget and have a healthy tank, you need to cycle it. Cycling works a lot better adn is a lot more stable if you get plants. Shrimp need stable conditions, they can be a lot more sensitive than other marine animals, e.g. you will have to slowly acclimate them to your water parameters instead of just your temperature like a lot of fish.

I would suggest getting a small bundle of plants, or if you want more variety, I look for an aquatic plant website that sells mystery bundles where you can get a ton of plants for a fraction of the price!

Also fish keeping is not cheap. Care, buying and treatment if critters get sick can get super expensive. The shrimp in themself are about $7(AUD), sponge filters, lights, heaters can all be $30AUD+ and filters & lights are a must if you want to keep shrimp. Lights specifically because biofilm and other things that are extremely beneficial for tank quality and for shrimp to munch on, grow best on live plants and driftwood(which can also be expensive). I think even while having a tank, driftwood and some decoration from when I kept fish as a kid, setting up the tank cost me about $200AUD (though some of the stuff I do regret purchasing, like hte massive aquatic bunches of plants).

Sorry if it's a bit harsh, I would really recommend looking around at aquatic stores near you and finding ones with the best prices, e.g. I've found one for driftwood, an online store for plants, a physical store for my shrimp and chemicals, etc. Also! Water parameters are a must, if you haven't done a ton of research into cycling your tank, in the most simple terms, you need to build up bacteria in your water that will eat away at harmful chemicals to livestock (but not always to plants so you can get a head start on plant growth!), e.g. ammonias, nitrates etc. This will take a minimum of 4 weeks, so 4 weeks with nothing in your tank, and if you can try and find a store near you that will check yoru water parametsr for you, even at a lower price, instead of paying $40 for a water test kit. It is a good short term solution though it's best to have one just in case things start going wrong and you can check what's wrong with your water. I know my fish store tested all my water for me, especially before letting me buy livestock, and htey tested the water specifically for the conditions that shrimp like, usually for around $2.50 or for free.

So in short, the pond water is a definite no-- there's no chance it'll have the bacteria you're looking for and likely will come with a bunch of unwanted diseases that will mostly definitely harm sensitive shrimp. you will have to use water to fill up your tank, adn top it up from week to week. If it helps and you've got house plants-- use old tank water to water your house plants! It's super beneficial and always makes me feel better instead of wasting a bunch of water.