Modern decks have become so deadly, that you really want to disrupt the opposing game plan early and often.
The common concept is that Legacy and Modern never change all that much. While there is some truth to this, as the best cards remain great, and often just get moved around into different configurations, there are always fluctuations due to small metagame changes. Let's look at two example decks, which were successful this weekend.
MKM Series Frankfurt
Andreas Müller became the Modern champion at the 613 player event in Frankfurt last weekend. Admittedly, after 10 rounds players were exhausted and he only had to win the semifinal to claim the trophy – after his opponents in the quarterfinal and the final preferred to not play it out. He won all Swiss rounds he had to play though, starting 9-0 and drawing the last round into first place after the Swiss. He also didn't lose a match in the Modern Grand Trial on Friday. A convincing feat, which proves that his deck is quite well positioned at the moment. The deck has a lot in common with classic Jund decks, but Lightning Bolt isn't the best removal any more, which makes dropping red altogether much more interesting. In “recent” sets we gained Hissing Quagmire as an alternative creature land to Raging Ravine and Blooming Marsh as well to improve the mana further.
Buying into such a deck doesn't really get cheaper by cutting the red cards, as they never were the problem. Therefore B/G is still an expensive deck, but all of Tarmogoyf, Dark Confidant, and Thoughtseize are currently quite „low“ compared to their price history over the years.
Andreas Müller – B/G Rock
Clearly a large part of the metagame rewards you for having a massive discard package and cheap removal, turning black into a very strong primary color – even when you aren't planning to cast Death's Shadow.
Such a black deck base helps fight all the combo decks, and the fast creature decks, and is especially powerful against the creature based combo decks, like Storm and Counters Company. It is much less helpful against land based strategies, like Valakut and Tron variants though, which have become the other format defining decks.
If you want to play (or invest in) a Modern archetype, which plays very similar to B/G Rock, but is much cheaper overall, I have you covered as well though. Here is the Mardu Pyromancer list, which made Top 4 at the the Team Trio GP Santa Clara at the same time:
Galan Falakfarse - Mardu Pyromancer
Despite using many different cards, the strategy remains similar. Cheap removal and discard back up a fast creature based aggression. While your creatures might lack a little quality compared to the Rock list, you have the advantage of being great at going wide with tokens, which is both great against aggressive decks like Affinity, but also weakens opposing spot removal significantly. Gaining access to white and red is a massive advantage for the sideboard as well, as Blood Moon shuts down those land based strategies and white has been known to have the best hoser cards for single minded decks in Modern for a long time now.
All the expensive cards in this list have recently been reprinted (Thoughtseize, Blood Moon, and Marsh Flats), making them very reasonable pick ups. Collective Brutality and Kolaghan's Command are strong cards even in Legacy, so you should have bought them a while ago already anyway, and if you haven't yet, it is about time.
Bedlam Reveler has been massively under-priced for its power level so far. Is it a cheap but large creature, which dodges Fatal Push, and red card draw all rolled into a single card. With the regular supply still being huge, I would look into Foils and Prerelease Promos instead. You can probably double your investment with those in a shorter time frame.
On Monday there will be the next Banned and Restricted Announcement, but we will most likely see no changes. They aren't touching Modern before the Pro Tour, and Legacy is in great shape - despite Deathrite Shaman's high relevance in the format. They won't ban any Energy card before even giving the new set a chance to affect the metagame, although they will probably have to in the long run. Vintage still requires a restriction of Mishra's Workshop, like it has for many months (or years?) now, but I expect them to put off that decision once again.
What are you expecting to happen on Monday?