Best would be a mix, but singular or heavily tactics training. Lower levels, tactics gives the biggest lift to your game. How much time a week would you be able to study?
Chess Mentor vs Tactics Trainer

I can get about an hour a day with out much problem. I know both would be important. I've spent a little time on the Chess Mentor, but I've focused a lot of time on the Tactics Trainer. I'm still not seeing a lot of what I should be for potential moves. I get a fair amount of solutions, but I've often had to study it so long - the time I took awards negative points to the solution. I want patience and I want it NOW. I really just want the most bang for my time. I love playing even at my level.

With your chess, I might be able to help you. Message me sometime.
I've sent a reply to your last message, but I'm not sure they went through. They're not showing in the thread. Did you receive them?

mthomas859 what I recommend is (and I hope this doesn't sound offensive) but learn something for your brain to judge the positions using like I use IM Jeremy Silman's chess imbalances and if you need to have it taught to you look on youtube for backyard professor chess because even though he's not exactly strong at chess he explains it really well because at least if you do that it'll give you something to work with strategically

Do the tactics courses on ChessMentor. You can't very well test your ability to recognize typical patterns until you've first learned what they are. Do the courses over and over again until you can 100% the lessons. Yes, occasionally wander over to the TT and try your luck, but recognize that until you have the tactical motifs down cold, testing yourself on them is of limited worth. This is a similar idea to Coach Heisman's concept of using Bain's Chess Tactics for students to drill fundamental patterns. I just think the Chess Mentor is more efficient.

Looks like great advice from more experienced players than myself here already, but I'll share my experience as a beginner who is enjoying the learning process too.
I think with the tactics trainer, it really keeps your tactical vision sharp, but you have to keep it "trained" and maintain it every day to keep it there consistently. Once, I did 1000 problems in around an 8 hour day. My rating shot up a good 200 points that week. My high at that time on the tactics trainer was 1670 and I think my blitz high went from 1200ish to 1440.
When I got soft and skipped a few days or weeks, my rating fell.
So I think the key to the tactics trainer is to do a good fair moderate to heavy amount of volume daily. Consistently. If you really want the best bang for buck with that.
One thing I wish I had done more of was the Chess Mentor.
For some reason, the "timer" on mine is stuck to something like 0.38 hours, but I've done around 850 lessons.
That's about 1/5 to having completed it.
Some of the lessons were beyond me, but I'm glad I soldiered through them because I feel I picked something up from the experience even if I couldn't explain what it was at the time.
Other lessons seemed easy or I should say, more natural.
I'll give you a good example of a lesson on Chess Mentor I took recently that I've been able to apply in my games with success.
It was a new understanding and skill I didn't have before the lesson.
The "course" I think took like 5 lessons and each were all about pawn storms.
The main idea was when to do a pawn storm (if you have more space on a certain side) and when not to do one but to move a piece instead.
The other ideas which were just as important were learning how to calculate when the move would be "fast" enough or if you needed to immediately bring a piece into the attack.
The idea there, was, that it's great to have the pawns rolling, but ultimately you'll probably need to give "checkmate" with a piece.
So that was important to take home.
Then, one idea that I found made that entire course worthwhile to me, (in addition to all the other gold nuggets I just mentioned above), was how to choose which pawn to advance based on your opponent's pawn structure.
For example, if there is a pawn advanced one square in front of your opponent's king, you could roll the pawn that would be able to latch onto it as a "hook" and then rip open the structure instead of allowing your opponent to defend against the pawn storm by keeping the position closed. If you are able to force the structure open, then they can't keep it closed and you'll be ready to go in for the kill (mate).
This is something I had picked up intuitively on my own just from watching masters' games but wouldn't be able to codify it into my own concrete plan with confidence aware of the important nuances if I hadn't had the opportunity to have a grandmaster teach me in the form of the Chess Mentor course.
So to recap:
*1.Train tactics trainer daily (preferably 50 problems or more/20 minutes) to drill home patterns you already know (the quickest ones in just a few seconds) and to learn new ones (the ones that you play through the solution moves to commit to memory and take the bulk of the 20 minutes time altogether).
If you are truly, truly hungry to take your game to the next level faster, then you can devote an entire day of several hours to doing as many tactics trainer problems as you can ie., 1000 problems in 8 hours maybe once a month. This will be your main "marathon day". Of course, this will come down to your own personal work ethic and time management abilities to juggle it all between work, family, etc.
Even if you can only do this type of massive training once every 2 months, it will still be very productive. In my opinion, there's no faster immediate gains than massively overdosing on tactic trainer problems for several hours or until you reach 1000 problems attempted, whichever comes first. *****In other words, if you sat down to play blitz right after, you'll find yourself capitalizing on opponents' mistakes that are rated a hundred points higher than you and end the games more quickly with wins because of tactics you had never seen before and rise up to start taking on more challenging opponents a hundred points or more higher.
(No other feeling like that in all of online live chess in my opinion. Every player, even the non serious hobbyist should try this approach at least once in your life if you can!)
On the other hand, if you are retired, on vacation, make your own work schedule because you have your own business like I do or on disability or some other type of set up where you have more time you can give to your training, then being able to do 1000 problems once a week will surely kick your understanding, playing strength and rating into high gear quickly.
Even if you can't apply all the ideas I've shared here exactly, I do hope maybe you can get the main idea from it and structure your own plan and create a routine that will help you get the most bang for your buck in terms of efficiency and results. *****My big shameless full disclosure disclaimer statement is that this is only from my own personal experience, so your mileage may vary depending on a number of factors. In other words, you may be twice as smart as me and get double the results in half the time.

There's a lot of good advice here and it's appreciated. I intend to utilize as much as I can. Even though I will probably always play for fun, it's more fun to win often. (One comment for Tom_Hindle - No, I don't find anything you said offensive.) Everything I've seen has been constructive - which is what I asked for. I'm open to other suggestions and "This is how I did it stories. Thanks for the input.
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Which asset would you recommend for a begining player with limited time, to make the biggest gains? Why?