My fellings about van Gaal are very mixed.
I know he is one of the most knowledgeable manager in football and have experience managing top clubs in different leagues and he usually do a great job. But his personallity could be a big problem. We can't really afford one more season like this and you never know which way it goes with van Gaal.
He is known by good work with youth, he knows how to deal with star players and usually gets the most out of his teams. We can modernize our aproach in games under him which we needed to do for a long time now. We lacked modern ideas of play since Queiroz left our club. Fergie was backtracking his aproach since he left to good old 4-4-2 which gave us problems in Europe in recent years. If we are honest even when we came to the final of CL in 2011 we were not nearly as good as our 2008 team. To be honest sale of Ronaldo didn't help either but our quality was dropping year after year. We lacked good youth players, our buys where not the best and our most important players was getting older. Our defense was one of the best back then and I think we made a big mistake in this season when we didn't give real playing time to our young CB's and this could hurt us in next season. In my opinion strong defense is foundations for every good team.
I hope van Gaal can turn this trend and we start building next big team.
His first job is to make solid back four which will play week in week out. For that we need one new left back and we need to decide which two of our CB's will be in the first team and we need to stick with it. For that we need to deal with our RB problems because when Rafael was injured we always played the CB in RB position and i think this was main trouble that we didn't have constant CB partners (along with injuries). I think van Gaal will promote one of our two youth players (Janko or Varela). I don't see any need of buying one mor CB especially if Rio stays for one more season as a backup. And van Gaal history shows that he rarely buy new players if he have good young players at his disposal with which he can work.
His second job will be to deal with our midfield. As i said his history show that he can get the most out of his players and i am looking forward which ideas will he bring to sort our midfield problems. I don't see us buying more then two mdfielders. We still have Carrick, Cleverley, Fellaini, Fletcher and Kagawa and Rooney can both play their part in midfield. For every mdfielder we bring in we must sell one which is already at a club and especially with lack of games if we don't get in Europa league. And i can't see leaving other than Fletcher and maybe Fellaini. Difference between good and great managers are that great managers have unimaginable ideas how to use their players and they make it work. This will be a big test for van Gaal and i am looking forward what he can do with it.
But his biggest job will be our attack. Our big problem is that we have numbers in this area but we somehow can't get the most of our players. And we have players which didn't show they are worth of playing for us in the last two seasons. We didn't buy wisely in recent seasons and now we have 4 strikers and we usually play with only one, 3 players which want to play as a number 10 and they are all to good to be on the bench and we lack quallity on the wings. I am looking forward how van Gaal will deal with our attack and he will have big headaches for this. I mentioned Rooney and Kagawa in midfield before just because we have to many players in their positions. I think Rooney can play on the wing too but i don't want to see anyone of the Mata and Kagawa on the wing because they are to big waste to play them there. If we play both Kagawa and Mata in the team i want to se Mata as a number 10 and Kagawa as box to box mdfielder. I noticed that to many people on this forum underrate Kagawas defensive work. And as i mentioned there are people that are just not good enough for our team. Young will have to go i think, Valencia is having troubles and i see him leaving to, Nani was constantly injured the last two years and if he can't get himself fit and in form till January transfer window i can see him leaving to. That will leave us with Januzaj, Welbeck and possible Rooney for wing options. I think we will need to buy one real quallity winger (quallity like Reus not Lallana). I think that Glazers want one star player signing this transfer window and we can do with star player on the wing. I can see van Gaal promote one of the youngsters too in this department (Lingard or Zaha if he can get his act together.)
I written all this to support my opinions that we don't need to many new players (3 or 4) and we can sell more than we buy especially without any europe games in next season. We need one good manager which will bring new fresh ideas to the club and which will be able to get the most of our current team. Van Gaal is really the best option for this as long as he don't fall out with everyone around him. I hope we can became once again the force we were in 2008 under him.