Yes I have to agree with the above steps to happiness
1. Plan carefully
2. Work out how much space you have first, I build my boards 900mm high and up to 1 metre deep
3. Take as much space as you can get
3. Build a decent base, there is no correct construction but I use 12mm MDF on a free standing table with legs and stiffeners good enough to walk on.
4. Get the levels right
5. Plan plan plan, a good idea is to look at the Set track plans book by Peco not because you want to use this system but it helps you plan and to buy only what you need.
6. Secondhand track is OK if it is fairly new, older Peco and Hornby is not as good as more recent items.
7. Never use secondhand rail joiners these are a sure way of stopping the flow of electricity.
8. You need droppers with electrofrgo points but really on here they are a bit of a fetish, take it from me the manufacturers do not expect you to place them every two feet or they would say so.
9. DCC again go this way later it is pricey and if you want blown decoders I have about 40 of them (a good few hundred quid here alone)
10. Work out what you want, as you see we have evolved our layouts, mine is honing in on Buckinghamshire on 19th May 1962 as this area was the place you could see almost anything on the railway and 1962 was the last great year of steam so that sets the stock, locos and the scene generally.
11. Secondhand rolling stock might be OK but often people sell things because they cannot get them working so caveat emptor in truth new from Hattons is cheaper than eBay and sometimes they even honour a warranty.
12. You can also go cheap on the scenery, is your layout a beautiful scene with a train running through or a railway with some scenery added, it matters but I would suggest a spot of feng shui for now and keep it simple.
13. Yes keep a bits box, I catch build items from left overs
14. tools, you'll need Xuron track cutters both side and vertical types, magnetic screw drivers, tap hammer for pins.
15 My advice is to leave any ball;last until later, I use Noch underlay which is expensive because it comes up clean, ballast is a pain so I suggest getting the layout reliable BEFORE getting carried away with the messy stuff, add later.
16. Allow track gaps for expansion a millimetre here and there.
17. If you want anything ask, I am happy to sell surplus dirt cheap as it takes up space for instance and I often sell at shows locally and that can be a good source.
18. If DC older Hammant & Morgan controllers are tough and will last forever.
19 Although lovely slow action point motors can be pricey, only fit them where points are out of reach you can add them later.
Planning will help keep the surplus down to a minimum so you buy only what you need, as to insulfrog/electrofrog, code 75 versus code 100 well that is down to you but as a general observation use R£ and R4 standard curves in corners and avoid flexi for now - remember
RELIABLE RELIABLE RELIABLE and you can really mess up with flexi when you bend it into shape
Hope it helps but generally the two posts above I am in agreement with.