Don't give up just yet :)
As you are using the Tapatalk app on your iPad, you don't need Photobucket or any picture hosting services. Try these steps.
1. On your iPad, go to the topic you want and tap '+' to start a new post, at the bottom left of your screen.
2. Type some text then tap the icon that looks like a picture with some mountains, next to the camera icon.
3. All your recent photos should be displayed in a grid. Tap the one you want to post. It will display full screen and you then tap 'Done' in the bottom right hand corner.
4. The app will then pop up a box asking what size you want to post the image. It doesn't matter that much but I generally choose the largest to get the best detail. If for some reason your picture is so large it causes an error, then just choose a smaller size. So tap 'Best'.
5. The app will then load up the picture into Tapatalk's photo library and will automatically create a correctly formatted link to the picture in your post.
6. Now all you have to do is tap 'Reply' in the top right of the box where you typed your post and the post will be added to the thread. The post I created with these instructions is just prior to this one in this thread.
Give it a try. Best of luck.