While many Alts are seeing a rise in value this is basically all off the back of BTC's rapid increase in value, in fact many Alts are bleeding value despite the fact their $ value is increasing. Lets take a look at ETH as an example of this:
ETH in June had a high of around $370, so say you had 10 ETH you could have cashed that out for $3700. Not bad BUT, it also had a value of 0.15 BTC so if you sold it then you would have 1.5 BTC.
Fast forward to today and ETH is a respectable $470 so your 10 ETH is worth $4700, $1000 profit by holding. It however it has massively declined in BTC value to 0.04 so you would only get 0.04 BTC for it.
If you would have sold The ETH back in June to BTC and did nothing else your BTC would be worth around $17000 so $13300 more profit by holding BTC rather than ETH. That is a big difference which would you rather have?
So to summarise ONLY buy Alts IF you are positive they can increase faster than BTC can otherwise you are just losing profit and in all honesty I don't see many of the top Alt coins being able to do that so I would sooner just hold the BTC in that case right now.
The main reason to buy an Alt is to increase the amount of BTC you hold so you can cash out of BTC when it hits an all time high like now. If your Alts are bleeding BTC value then there is no reason to hold it you might as well just stick with BTC and save yourself the risk and have better gains.
So what should you buy when looking for Alts if you want to increase the amount of BTC you hold?
Well my preference is low marketcap Alts that have potential to easily x2 or more in value quickly otherwise you are just losing BTC. Something like ETH has such a huge marketcap already it is not going to x2 overnight, however these low Mcap coins do have that potential. Something can easily go from $1 million to $2 million very quickly and double your BTC. If you must go with the top Alts then make sure they have something big coming soon or you will just be losing profits against BTC.
I'm not going to give any examples of coins I like in this post as I don't want this to be a shill post, it is purely educational for the new members of the Crypto Community to help you all get off to a better start in the exciting world of Crypto Trading.