My personal experience is start small and build your knowledge base by accretion, and practice weekly (daily is better). Firstly, think about the overall organising principle you want to build in your mind to organise what you're learning. For my botanical exploits, it is Latin genus names. I only have to think of the Latin genus name of the plants I've learned so far (e.g. Lomandra, Dianella, Acacia, Leptomeria) and all the information I've internally attached to that name comes pouring out. You can organise information by writing in a book alphabetically or topically (e.g. grasses, trees, flowers, vines), graphically (attach each thing you're learning to a particular picture, colour etc) or locatively (attach each memory to a set location you can access daily, e.g. a tree in your back yard with notches cut in the branches, a memory board, a window sill with marks on it, a beaded necklace, or landmarks on your daily walk, etc).
I have a four step process of attaching information to each botanical I am trying to memorise.
ID - Learn key identifying features: common names, leaves, roots, flowers, seeds/fruit, bark, seasons, colours, variants, Latin taxonomical name(s); locations.
FOOD - Which parts can be eaten, if any? Which parts should be avoided? Any special processes involved? Recipes.
MEDICINE - General use, e.g. antibiotic, antihistamine, diuretic etc.; extraction techniques, e.g. poultice, tincture, tea, salve etc; dosage, e.g. 1 tsp dried leaf per cup boiling water, etc; mechanism of action (this last category requires advanced knowledge in chemistry and cellular biology), e.g. ACE2 receptor binding agent, protease inhibitor.
OTHER USES/INFO - Fibres, cordage, shelter, ash/charcoal, toxins/poisons, look-alikes, etc.
Let me illustrate. When I first started my native foods journey two years ago, I could only ID a few common Australian plants I learned during my childhood: lomandra, eucalyptus lerps and lilly pilly. Let's take how I have expanded my knowledge of lomandra over the last 2 years.
ID - I started with consistently identifying lomandra. A 1.5-2m (5-6 ft) tall, strappy grass with spiky flower heads; green peppercorn-like seeds which turn orange (some species, black). Every time I went for a walk around my local area, I would ID which tall strappy grasses were definitely lomandra, and which strappy grasses were NOT lomandra (even if I could not ID the look-alikes at that time - I knew they were NOT lomandra by the key identifying features). I recorded in a book the general locations I have found lomandra so far. This last step of recording locations becomes less important with truly common plants, but uncommon or rare plants should definitely have their locations recorded so you can find them again if required.
FOOD - Once I could ID lomandra at will and tell it apart from look-alikes (even if I could not ID the look-alikes), I researched food uses of the plant. Starches and carbs in the white leaf bases; seed kernels which can be harvested in Jan-Feb and ground into flour. I then wandered my local area and harvested these parts, trying them out and seeing how they can be prepared and cooked.
MEDICINE - I have not yet found any medicinal uses for lomandra during my readings. However, I noted the green seed husks when crushed in water emit a very fragrant odour. This is set aside for future research.
OTHER USES/INFO - Strappy leaves used for cordage and basketry. Leaves could be confused with Dietes lily, which is poisonous.
Practice and continual reinforcement is a key. Go for walks around you local neighbourhood or in local national parks and start with the basics: ID plants. Once you start building up a bank of reliable identification experience, start explaining (to yourself or whoever is with you on your walks) what FOOD uses the plant has. Once you can do this without referring to notes, start adding MEDICINAL and OTHER uses or info, such as poisonous look-alikes (if any). In this way you continually accrete information, building on what is already there, whilst building a reliable system of instantaneous recall so the information is ready for when it is needed. Obviously everyone has their own ideal method for learning; mine is pure brute force and reinforcement by repetition. Others prefer making nonsense narratives, ditties or poems to help them remember.
Half the excitement, besides getting around in nature, is when you come across a plant and think to yourself, "I'm pretty sure this is [plant]...." Take a photo with your phone, go home, skim a botany book and aha, yes, I was right! Or no, I was wrong, it was this other one.
Learn. Recall. Build. Recall. Master.
Do this for a few decades and you'll become a walking encyclopaedia, just like the elders of the ancient cultures I admire and respect (as we all should).