My advice to new to the garden, ALWAYS buy bigger. As a self admitted "analog dinosaur" I've been pushimg electrons down the rails since 1995. My empire has grown in pre-planned stages, and one not planned when "She Who Must Be Obeyed" said "I want to send a train off into the distance and it not come back for a while." That one ran along the back fence weaving through her roses (180 ft) and turned to weave amoung her fruit trees.
Transformer: Learn from my fail. As time went along each exoansion created a need for more power. My storage shed holds 5 working transformers that were not big enough to handle the expansions. Guesstimate your power requirements five years from now, find a transformer to fill that need, then buy the model two sizes bigger. You will save money in the long run.
Switches (Turnouts): Buy more than you need for you beginning plans. Position them as 'stub end sidings' that can become expansion points for later construction. In my case initial construction was a basic oval around the Koi pond. Switches were installed for future track yard, future bridge to the Chateau atop the waterfall, etc. When installing switches remove the 'slip joint' rail joiners and repalce with rail clamps. Domestic and nondomestic wildlife have a tendancy to leave "gifts" on the switches, and dirt and small rocks also collect there. Rail clamps allow you to lift out the switch without disturbing any of the rails so you can easily take the switch to a work bench for complete cleaning, or repairs if needed.
Rail joints: As the ground shifts under our empires the standard slip joint connectors will become mis-aligned giving the oportunity for derailment. Use short setional track where you must, but longer 'flex' rails when ever possible. For my longer runs I soldered two 10 foot sections together for 20 ft pieces and joined them with rail clamps to the next section. The fewer joints you have makes for less oportunity for wheels to 'pick a joint' and derail.
Feeder wires for rail power: Every fourth rail joint has worked for me. forty feet for the 10ft rail sections, MUCH shorter for the areas with sectional track.
Reference books: It has been a long time since I looked at any, but, in my opinion, these pages give a lot more information than any book. A good book will give the writers opinion on any issue, this forum will give many different ideas how we all solved the issue. Pick a couple books and then research the issue on these pages for other ways to solve.
Word of advice, never ask "what is best . . . " on these pages. Best has many built in problems; your local microclimate, your soil type, wildlife issues, and many more. What is best for me may well be the worst possible choice for you. Over the years that question has caused a few heated discussions.
Having said all of that it is time for you to get outside and play in the dirt.