Dwarf marigolds are easy to grow from seeds. Don't put in too many, they may all germinate! However, they do not grow all year. Summer is their favorite time of year. Put in sunny window and cover with saran wrap til they pop.

I don't think white picket really goes with your homestyle. you can keep it reasonable by only doing the side to the left. I have included some other types of fencing that might work better for you. Just to give an idea and there are even more on house. Of course, just plants are always great too. or you can start with fence til plants grow.

Here's an alternative to a recliner that you may not have considered. It is a snuggle chair with matching Ottoman. It swivels too. Available from Plush Sofas. I love ours... So relaxing and there is room for two adults. Available in leather or lots of other fabrics too. I took this photo of the shop display one before we bought ours...

I would consider a small retaining wall perhaps 2-3 planks high this will provide support to the bank but also allow the pathway to remain clear and formal. The ferns seem to be doing well but could do with a tidy up. I would also prune the tree so it allows a bit more light into the section to help prevent dampness, you also want to take it away from the house, without destroying it's natural shape. As ferns seem to naturally want to grow there, you could continue that theme. Perhaps some other shade / cooler temperature type plants with some flowers could be a good addition. I am not sure which plants can tolerate the cold Dunedin winters, so you best contact is your local garden centre. You want plants that are lush all year round. Also have a look at other plants growing in the neighbourhood as that will give you a good idea of what does and doesn't do well in your climate. Good Luck.