I would like to create a very small circular layout and run the engines. The problem is that I don’t have any track nor a transformer. Also, the trains haven’t been run in probably 3.5/4 years.
what would be the best steps to take? What kind of track do I need to buy? Do I need to buy an MTH Z4000 transformer? I remember using this transformer as a child but I don’t have it anymore.
ive read that this new DCS system is something that I may be able to use from my phone but I have no idea where to even begin. I haven’t ran any trains since I was a kid and my dad was there to help me
all of the engines are MTH and some are from the early to mid 2000’s
Well, to your questions:
From the description, it sounds like the trains you have will run conventionally, relying on the transformer's throttle setting to vary the speed by varying the voltage, and control direction. If the trains were well maintained before they were stored, I don't think any pre-running maintenance should be needed after five years or so, at least to test them out, but a very light application of lubricant on the axles and bearings wouldn't hurt (test running will tell you pretty quickly if more is needed!)
To create a simple circular layout, you first need to select and purchase the track. I would first consider traditional 3-rail tubular track in O-27, of the type familiar to anyone who ran trains as a kid. Track of this type is inexpensive (a couple of bucks per section for new repro, as cheap as fifty cents per section used) and should serve you well. The other major option is Lionel FasTrack, which is more expensive (about five bucks per section new, a bit less used) and a bit noisy in operation, but has a simulation of ballast molded in and thus is a bit more realistic. If you plan to keep smallish postwar rolling stock, just about any radius track will do, but if you will want to run larger engines or cars, you may want to get larger radius track.
Unless you plan to run more than one engine at a time, most likely any used single-set transformer will do you just fine. You can usually find them for $20-50 or so at any local hobby store, or from on-line sellers (though shipping will up the cost!). Multi-throttle or larger transformers would be overkill for your plans IMHO, unless you definitely plan future expansion. If/when you do upgrade your transformer, the smaller transformer(s) can be repurposed for powering accessories or separate loops.
I run entirely conventional and PW, and do not have (and have not used) the more advanced control systems, so I will not attempt to guide you, other than to say that you will need to spend hundreds if not thousands to set up such a control system, and IMHO again that's massive overkill for an around-the-loop small layout. Yes, the speed and directional control will be better, and allow you to access any on-board sound and lighting option on your existing rolling stock *not* available running with conventional control, but be aware that that will be a deep rabbit hole to dive into, which you can (and IMHO should!) postpone until later, until after you decide to dive deeper into the hobby! When you do, be sure the control system will be compatible with your current equipment, or reconcile yourself to replacing all or part of your existing rolling stock.
In any event, good luck, and welcome to the hobby!