You'll be changing the oil and filter on a regular basis and that often happens during any dealer service. You mention Toyota so I'm assuming you have a V6 with the Toyota engine. Here's a Forum thread giving advice on the appropriate V6 oil filter:
Has anyone ordered parts through the Lotus site? parts.lotuscars.com It redirects you / or tries to redirect you to your closest dealership to order parts. Basic searches for “oil Filter” don’t always work and after email Lotus support and them giving me a part number I was able to find an oil...
www.emiraforum.com
I purchased a case (10 filters, if I remember correctly) from my local Toyota dealer, at a discount. If you're getting the dealer to change the oil for you, they should do so, using a filter you supply. I'd suggest you change the oil plug ring each time, as well.
You can also buy your own oil, which will typically provide further savings. The manual specifies the oil type but there are Forum threads where people describe the other oils they use.
Other than those 3 things (filter, o-ring, oil), there's not a lot of "spare parts" you'll regularly have to replace. You might consider topping up your own fluids (windshield washer, radiator...are the more common ones) and telling the dealer they don't need to check any fluid levels (avoiding a dealer charge).
Without access to a local Lotus dealer, I'd encourage you to DIY as much as possible, perhaps starting with an OBD II scanner that works with the Emira, so you can investigate any codes that come up, then search this Forum for helpful advice. The second scanner I purchased worked the best, since it lists "Lotus" as a car manufacturer in its software. It was also much cheaper than the first scanner I bought. The
BlueDriver OBD2 scanner is the one I recommend for the Emira. Amazon sells it, so it's easily obtained. Others are happy with it, and it's simple to use. You'll need to download an app on your smartphone, but the app is free. Good luck!