I'll just try to give you some advice on visiting the Oktoberfest.

The event has seen a big surge in popularity in recent years. Nowadays it is virtually impossible to get into any of the "tents" after 5pm. On some days (weekends!) the doors may even close at noon - for people that don't have a reservation. You don't really need a reservation that early, but once all the tables are taken, no one without one is allowed inside.

Without a reservation, you can do what a lot of the locals do: visit the ""Mittagswies'n". Get there at about 11am and find a nice table out in the sun. If the weather sucks, find one inside. Noon crowds are very much weather dependent. Have some beers and food before the huge crowds arrive and leave when they do.

For the noon version of the OF I like the Ochsenbraterei. But most others will do as well.

If you really want to go at night, you absolutely have to book a seat at a table and prepay for the equivalent of 2 liters of beer and half a chicken. But you can use the vouchers you receive for whatever else you like. Which should cost about EUR 35. Most people/groups/companies book entire or multible tables, but there are lots of tour operators which have offers for individuals. They are usually a bit more pricey.

But forget about getting into any of the major tents by just showing up at night. The last time that was possible was around 1995.