@puppysuicide101
Ads aren't always available, sometimes the ad bucket is empty and has to be refilled so you have to wait.
If you're on android i believe you can get a refund within 2 hours through the playstore if you want your money back.
You can also do Google opinion rewards surveys for play credit to avoid spending actual money, not a huge amount but they don't take long and they add up to 2 or 3 premium plants per year.
I have been playing a long time and tell you now you're going to need a lot of coins, if you google 'pvz2 favourite plant' there is a chart showing the costs in seeds and coins for each level and some of those upgrades can cost up to 100,000 coins and that's before you start upgrading through mastery.
I suggest you build yourself up a stash of coins and gems and only upgrade the plants you use instead of useless ones like em peach.
Penny's pursuit is a good way of getting extra coins but don't get greedy because extra perks and security gourds can eat through gems at an alarming rate.
If you are having trouble killing zomboss you can always ask for help.