A couple of things about tarantuals since this will be your first pair. You generally don't want to buy a male and female of the same size as the males will usually mature and die long before the female matures. Its an even longer process than with mantids. Unless you are getting breedable adults your best bet would be to buy the female now and let her mature (it may take a few years) and then look for a mate. No need to worry about the female dying before you can get a male as they live for many years with proper care. If someone tries to sell you a male and female from the same sac don't do it.
Keep in mind if you buy unsexed animals you run the risk of getting a male which is not going to live as long. If you are buying guaranteed sexed animals (larger ones) they are going to be more expensive, especially the females.
Unsexed slings are always going to be cheaper but you don't know what sex you are getting and it will take longer to mature obviously. My personal motto is to beware of people selling mid size spiders 2-3 inches or over as unsexed. I'd say about 90% of the time if I bought an unsexed spider of that size it turned out to be a male. Maybe its just the cynic in me but I think a lot of people sex the spiders, if its a female they say so and if its a male the say its unsexed. Of course I don't know how to sex them and I do sell spiders of that size as unsexed so essentially I just told you not to buy a spider of that size from me but if you chose not to I would completely understand why. Many times people won't declare it a male or female unless they can see the freshly molted skin and see for themselves and if a spider hasn't recently molted for them they may honestly not know (that's the spot I'm in, when I do get spiders old enough to sex by the molt I have someone check them out)
I'm not sure how much money you have to spend but I will give you my top three tarantula species. Not necessarily my favorites but the top ones I recommend for beginners
1) Chaco golden knee (Gramostola pulchripes)
Pro's- Very pretty, very hardy, relatively inexpensive, very docile, very easy to care for, very nice for displays (unless you want a pet spider web tunnel) mine never flicked hair.
cons- kind of slow growing, not a huge potential for money making (not saying that is your goal) as they are fairly common but they do sell well even if at a lower price.
2) Brazillian Black (Grammostola pulchra)
Pros- Beautiful jet black spider, very hardy, very docile, nice for display, mine never flicked hair, nice money making potential for slings
Con's- Not terribly expensive for smaller unsexed slings but older specimens can be pricy, especially guaranteed females. Slow growing so unless you spend the money for older specimens you will be waiting a while (a few years at least ) before you can think about breeding
Mexican Red Knee (Brachypelma smithi)
Pros- very pretty, docile in that hey rarely bite, a little more expensive than the chaco but usually less than the Brazilian Black. Nice money making potential because they are so popular but not prohibitively so. Nice display animal
Cons- Again, rather slow growing so getting slings will mean waiting for breeding. Mine always had a tendency to flick hairs. This species never bothered me as much as some but everyone reacts differently.
My favorite species is the Mexican golden red rump (Brachypelma albiceps) but it is rather expensive and hard to find. I also find mine to be a bit less docile but I do handle it occasionally. Mine also flicks hairs readily. I think its the prettiest T available but the price and being less docile keeps it off my recommended for beginners list but it may make the top 10
I know there are others out there that would make my list of docile, hardy, relatively inexpensive nice display (most of the Aphonopelma species come to mind especially A. chalcodes) animals but the three I listed are my top 3. If you don't mind a little more aggressive animal and won't be handling it then there are a lot more that fit the bill. Acanthoscurria geniculata, Nhandu chromatus and Nhandu coloratovillosus come to mind
all these are terrestrial spiders, if you want an arboreal one the pink toes (Avicularia sp.) are nice , especially A. versicolor. If it weren't for the slightly more difficult care requirements (not exceedingly so however) they would probably crack my top 5, as it is they would still be top 10
Anyway, sorry for the long post. I think tarantulas are great pets and I just wanted to give you a few tips and suggestions. I'm sure you've done your research if you have any questions don't hesitate to ask. I'm not an expert by any means, I just know what I like and i know a bit about what makes a good pet for a beginner.