Be bold and make changes to the shape of your lawn and beds - if you don't need the lawn for kids to play on for instance, cut some new bads, changes the shape of your lawn to extend in to what was the lawn or put some raised beds in.
By some young trees - I love all the trees I put in my garden and wished I had thought about adding them years before I did. I have put an acer, 2 different amelanchias, 3 different silver birch, one rowan (my least favourite), 3 magnolias - an Elizabeth (yellow - one of the best trees in the garden) , a Susan (purple) and a white stellata (shrub) and a rowan (not too impressed by that)
Move things if they are not flourishing - some things do take a couple of years to get started - my camillia has been in 3 years and not flowered yet but looks healthy. The acer struggled in the front (north facing) for about 7 years and wasn't happy - I put it in the back garden with more shade and within 18 months it was a completely different tree - it's an absolute joy now.
I have had 4 tones of soil improver delivered over the last 10 years - honestly - it goes nowhere - when you heap it up you wonder how you are going to disperse it all but somehow it gets absorbed. I also had a couple of tons of tops soil for some raised beds.
You can never have enough water butts - I have 4 and prefer to water things early in the morning when it's going to be hot - conventionally I think most people water in the evening which is a nice relaxing thing to do.
Not all shrubs and trees last forever - if they look past their best don't have any qualms about taking things out - I quite like it when my wife points to something and asks me to take it out - it's a bit of exercise, you have to be patient - a mattock is essential but you can't use brute force to get a big established plant out - you have to be smart and feel for all the roots that need cutting, especially the tap root - usually right under the trunk going straight down - they are wire-y adversaries.
I always look for bee friendly plants - I love being around bees.
We have a lot of climbers - honeysuckle, clematis, jasmine and roses. It's rewarding watching your plants grow and do well. I love wilder looking things like foxgloves and I let poppies self seed all over the place.
Also - walk around your local area to see what grows well on the assumption that they have the same soil type. Take photos and use google lens to identify them.
You will need to look up when things need pruning - be brutal - my Cornus (dogwood) looks great in the winter - bright orange stems - does better the harder I cut it back in the spring. Witch Hazel also looks great in winter when the garden looks dead and colourless.
Just enjoy it. Be bold.