I'll start somewhat off-topic. Since Bitcoin is supposed to be at the first half of a bull run and still the price went down heavily this week, why not Bitcoin?
However, this is a speculation and don't invest just because I said so. Do your own research and decide based on what you think, I don't want to be held responsible if my logic is incorrect.
Now on-topic. Doge has quite a big tail emission i.e. inflation, hence imho its price is mostly speculated. XRP is even worse, since it's pre-mined, I expect the price being heavily manipulated by Ripple. So if you want to invest into altcoins, maybe you look around more advises and other coins.
Doge is perfectly design with endlessly decreasing inflation rate.
ie every year x coins
so year one to year two x turns to 2x and inflation is 100%
but year 10 you have 10x coins and year 11x inflation drops to 10%
and year 20 you have 20x coins with year 21x inflation drops to 5%
this is a very very very very good design for p2p and for mining.
miners always get a reward of 10,000 coins they know this and can plan for it.
and the inflation rate endlessly drops and drops and drops.
far far far far far better than btc for p2p
but the op wants to invest. and the back end inflation which will be lower than dollars does not match btc.
most people do not understand that btc had a very high rate of inflation years 1 to 4.
that dropped bigly in 2012 with first ½ ing
and the following 1/2ings.
if op wants to hodl more than 20 years he should do a mix of btc and doge.
fuck ripple it is pos which is a joke. (i am anti pos all pos)
now my opinion on the three coins above is not me giving advice it is an opinion.
I do have advice here it is :
do not invest more than you can afford to lose. furthermore just because you can afford to lose it in you own mind check with trusted friends and relatives as to whether you can afford to lose it.