Come over to the Mumsnet Gardening topic everyone, we don't bite 
Start a thread and post a few pictures if you can, you'll get loads of straightforward advice and beginner plant recommendations. Keep asking questions and starting new threads if in doubt. Photos are always appreciated!
I found mumsnetters advice invaluable and it stopped me making expensive mistakes. Plants for shade, (un)suitable conditions for ericaceous plants (rhododendron, camellia, azaelia etc), evergreen planting for winter interest were a few things I didn't have a clue about for example!
Most plants will tolerate being moved (carefully) if you've put them in the wrong place, but it saves a lot of time and effort if you get it right-ish first time. It can be disheartening not knowing why your plants are failing. You end up believing you're just not cut out for gardening full stop when it's often a really simple fix 
Without seeing photos I'll make a few suggestions in addition to those already posted:
I've been enjoying Morrisons lately for cheap, reliable plants - many of which are really good for wildlife especially pollinators (save the bees!) Worth checking out if you have one nearby.
When you identify a plant that would do really well in a particular spot it's worth buying two or three of them and spacing them out within the border/s. This helps fill the garden more quickly and introduces a
pleasing repetition/ rhythm to your planting scheme. Honest!
Shrubs and climbers are important for depth/ structure in your borders. If everything you plant is quite small (e.g. less than 20cm height) at its mature height (i.e. maximum size) your garden can look quite flat. If you fill your boundaries (fences/ walls) with climbers you add visual depth, interest and habitat for wildlife. The edges of your space are softened. Ditto with shrubs - the height they contribute makes the garden more interesting as you can't see all areas at once.
My garden isn't massive so I try to introduce height via climbers and choose shrubs with a max height of less than a metre (or else slow growing) so that I'm not forever pruning!
I'm massively still learning in this respect, there's loads of fascinating and often straightforward trickery you can deploy
Height is definitely important for visual interest. If your plants are taking a while to establish you can experiment with wigwams/ obelisks covered in sweet peas for example (annual so they will die at the end of summer) as well as planters of shop bought annuals placed on windowsills and hanging baskets. The more of these you have the better the overall effect imo.
Unfortunately a lot of gardening takes time. Time in the sense that you need to be out there every day checking things are growing okay, identifying pests, watering etc. Basically identifying any problems while they can still be corrected and before things become terminal! BUT there are sneaky ways of making a garden more low-maintenance. If you're upfront about your time constraints we can advise accordingly!
The How to be a Gardener series was on YouTube at one point I believe. Did they ever release it as a DVD? If not I've googled and found series 1 on the Daily Motion website. Quality is not great but the audio is fine
Once you start to learn about plants the RHS website is invaluable. I often google 'RHS plant name' to find out quick info about a particular plant (often quite basic!) It's the equivalent of the label on the plant but a bit more in depth. The pruning advice is a bit more complicated so I'd leave that for now! Loads of other useful beginner info on there, I just haven't had time to read it!
Don't be disheartened about plants taking a while to get going. A lot of my garden has taken 2-3yrs+ to establish. It's rubbish looking at twigs for the first year or so! This is where annuals (bedding plants and seeds that you can sow out around now - watch out for slugs) can come into their own to make your space a bit brighter in the meantime.
Sorry for the essay! There's so much more I could write