I'll assume that you're in the US?The best version for the original anime is going to Anime Limited's Blu-ray release, given the remastered picture and sound quality, which is stunning. Plus, this is unedited:
https://www.amazon.com/Cardcaptor-Collectors-Limited-underneath-Blu-ray/dp/B0B1K3BMYY

However, this is expensive! It is also locked to Region B, so you will need a multi-region Blu-ray player.

The best version for the Clear Card arc will be Funimation's release here:
https://www.amazon.com/Cardcaptor-Sakura-Clear-Complete-Blu-ray/dp/B0892HNGRT

As already mentioned here, if you want the movies, you'll have to buy them separately.