While the following is not financial advice, and is something that I myself am working toward since I didn't start out with the following plan, it does seem reasonable for combining the prudent stability of investing with the fun of riskier trading. 

Step One: Establish Monetary Commitment Over Time

A lot of people, especially those new to investing, decide that they have X amount of dollars to commit and they commit X amount of dollars immediately. I highly recommend against this approach. Here is one example of how one might invest instead:

1. Determine total amount one is willing to spend over a given time span. Let's say $1,000 for the next six months. 

2. Commit to half ($500) initially. 

3. Commit to (roughly) 20% ($100) more for months two, three, four, five, and six.

Justification: First, if a financial emergency happens and one thus really didn't have $1,000 to invest, this allows half of that to deal with the emergency instead of having to quickly decide what cryptos need to be sold, which can result at selling at a loss. Second (with no financial emergency), it allows one to do something that people often forget in investing that helps make money . . . averaging down. If after a month that $500 is now $400, buying $100 more at the reduced price allows for a smaller overall get-in-the-green gap (doing nothing = having to gain 25% from the $400 to get to $500 vs. averaging down = having to gain 20% from the $500 to get to $600). Third, if one or more cryptos made gains in that month and one wants to cash out those profits, one has $100 to either invest in the next runner one has in mind or to re-invest in the profitable one after its price drops a bit. Fourth, if the whole investment went up, the $100 can be used with greater freedom/less risk if one wants to expand the number of cryptos one is invested in.

Step Two: Research! DD is Everything

Even if one is not taking my advice of diversification in step three, and is only choosing to put money into Bitcoin and Ethereum, understand price action and when a good time to enter into those investments is clear in your mind. On the other hand, if one is following my advice in step three, researching "alt-coins" is absolutely required. One quick tip about this is distinguishing between those coins or tokens that sites like coinmarketcap and coingecko have a fair amount to say about in the overall description vs. those they do not have too much to say about. It indicates that those sites have done more research themselves about the ones they have specific information for as opposed to those with limited information that is also vague. Also one should be able to find articles written by analysts about coins or tokens under consideration . . . such articles are not sufficient for investing in, but they are necessary. Third, check out the websites for these coins or tokens under consideration. Look at things like their ecosystem and their roadmap. Projects that are going at a good pace, with things coming up, indicate legitimacy (where legitimacy means one is unlikely to lose everything by investing in them).

Fundamental rule: know what you are buying.

Step Three: My 40/20/20/20 Crypto Portfolio Ratio

Again, not financial advice, but if the first two steps seem sensible, then this should too. One might want to alter those percentages somewhat, but I highly recommend not going below the 60/40 (first two/last two sums) or the 80/20 (first three sum/last). 

Here's the idea:

Bitcoin = 40%

Ethereum = 20%

Ten of those cryptos in market cap rank 3-50 = 20%

20 of those cryptos in market cap rank 51-X00 = 20% (here my idea is to select 15 from 51-200, and then one each from each of the next 100 for real wild cards)

Justification: 60% of the total crypto investment is devoted to the absolute guarantees to grow for years or decades to come. It is possible that within a year the $300 (to use the above dollar amount) invested here would be worth $500 or more. Another 20% if devoted to those that are also likely to see significant growth without hardly any risk of total collapse and failure. The crypto universe is truly bigger than Bitcoin and Ethereum. Blockchain technology and niche use cases and specific priorities for application of the technologies involves guarantee depth to the world of cryptocurrency. Finally, the crypto universe is not that much bigger than those outside the top 50 in market cap. There are about 15,000 cryptos out there. I am willing to say that 90% are not worthy of any consideration (not necessarily the bottom 90% at any given time, but 90% of the total). 

That would be $200 in Bitcoin, $100 in Ethereum, $10 in each of Solana, Cardano, Polka Dot, Decentraland, Cosmos, etc., and $5 each in AMP, Chiliz, Ankr, etc. 

Over time rearranging, expanding, consolidating, and whatnot would take place, but I do see this as a mix of prudence and fun, a whole bunch of stability with a dash of risk.