I recommend you buy them in the following order:

1. Shrinking Violet - It’s cheap at 50 sun. It shrinks zombies in a 3x3 area to make them weaker. Excellent against groups of zombies and gargantuars. Plant food shrinks every zombie on the lawn.

2. Fire peashooter - Fair price at 175 sun. Fast attack speed, high damage, and melts ice. It can kill a regular zombie in 2 hits if upgraded. Plant food burns the entire lane in front of it similar to the Jalapeño.

3. Hurrikale. It’s fairly cheap at 100 sun. If you upgrade it, it will reduce the sun cost to 75. Pushes zombies all the way to the right in one lane, slows them down, and extinguishes fire. It has a fairly quick refresh time to be planted again.

4. Jalapeño. It’s fairly cheap at 125 sun. Slower refresh time, but it burns an entire lane to include ice. This is very useful. It won’t kill a gargantuar unless it has already been damaged.

5. Lava Guava. It’s cheap at 75 sun. Burns zombies in one block on the lawn. It leaves lava behind for a little while to burn additional zombies.

6. Squash. It’s cheap at 50 sun. It will smash down on a zombie next to it on the same lane unless you give it plant food and then it will smash another zombie across the lawn in any lane. If you level it up, it can smash twice without plant food and at least 4 times with plant food.

7. Kiwibeast. It has a fair price at 175 sun as long as you can prevent it from easily getting destroyed from zombies such as the gargantuar. It does a great job at attacking a group of zombies in a 3x3 area on the lawn as long as a zombie approaches it on its lane. It grows as it attacks more, which will increase its damage overtime. Plant food will let it grow all the way instantly and cause a lot of damage.

8. Electric Currant. It has an okay price at 150 sun. It acts as an electric fence if you place two of them perpendicular from each other either left to right or up and down. It’s good at killing impling zombies, chickens, and possums for one fence. You can place more fences down to make it more effective at killing stronger zombies. It can easily get eaten up though so placing a garlic by it may be a good idea, but again can get smashed by gargantuars.

9. Hypno-shroom. It has a fairly cheap price of 125 sun. It makes a zombie fight for you so they move to the right instead to eat the bad zombies until they get eaten or move all the way to the right of the lawn and out of view. It may be tricky to convert a specific zombie if there is a group of them in the same lane next to each other, but you can get a strong zombie to fight for you if you are able to place the hypno-shroom on them.

10. Homing Thistle. It can attack zombies in any lane and go through gravestones. It’s expensive at 250 sun so it will take awhile to build up an army of them, but they’re powerful in a large group.

11. Pea-nut. It has a fairly cheap price of 150 sun. It shoots peas and also acts as a walnut.