Speed paste is a name generally given to d,l-amphetamine sulfate, or d-amphetamine sulfate although in some areas it can be d,l-methamphetamine (sulfate or hcl), generally it is a paste because things like glucose and water are added to it as a cutting agent, as it still dissolves in water, but isnt generally "smokeable" like your classic methamphetamine hcl would be.
It's called "base" because, and again this is a few reasons, either its d,l-amphetamine base (as in, not the acidic sulfate form), which the amphetamine base is a oil at room temp, so then glucose is added to make it more of a solid transportable/easily to dose form. From my experience, but this is hit and miss, when it is called "base" it is generally a hype/sales tactic and not indicative of the quality of the source at all. Could be absolutely stunning nearly pure d-amphetamine sulfate mixed with glucose/water to goop it up kind of giving it that stereotypical look where 50mg will have you geeking for days, or it could be 1-5% (due to suppliers/vendors cutting it over and over as it switches hands and they try to maximize their profits at the expense of their products quality as well as the satisfaction of their customer base)
Little to no effect after .25g? so 250mg? That sounds then, like your vendor ripped you off. I would write in a mail to him, letting him know that what he sold you was inactive, and demand a refund or perhaps for him to reship some quality, and barring that if he is unwilling, perhaps (if this is an option on the website you used) report him for bunk product and try another vendor.
Generally, true "quality" amphetamine paste would be active at 1/10 that amount, so .025g (25mg) in a non tolerant user.