What tickets to buy when visiting Disneyland Park California?

If your budget can or will afford, I strongly suggest to buy 3-day Park Hopper Ticket. There are so much to do in both Disneyland Park and Disney California Adventure Park. For the first and second day, I suggest to stay in each park then do a hopper on the third day.
Both parks have plenty of activities, shows, rides, etc. and also plenty of long lines. Adding a Disney MaxPass when buying your tickets is WORTH it. It only cost $10 a day per person. MaxPass includes PhotoPass and FASTPass. If you buy 3 day park hopper with Maxpass it will also include the Magic Morning Early Access.

PhotoPass 

• Your photos will be taken by Disney Photographer on designated locations. Unlimited!
• Unlimited downloads of photos to your devices.
• You can download and share it right away.
• Your photos will be available on your Disney account for a month. So you will have enough time to download and do whatever you want with it.
• https://disneyworld.disney.go.com/guest-services/photo-pass-service/

FASSPass

• Allows you to skip a long lines on selected rides, attractions, shows, and character greetings.
• Check availability of what you want to do because this is not guaranteed on some.
• You can reserve your spot using the Disney App - It will save you a lot of time.
• Just having to save time by not waiting in line is AWESOME!
• https://disneyworld.disney.go.com/fastpass-plus/